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Climate and Average Weather Year Round in Waltham Massachusetts, United States

In Waltham, the summers are warm, the winters are freezing and snowy, and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 19°F to 83°F and is rarely below 4°F or above 91°F.

Based on the tourism score, the best time of year to visit Waltham for warm-weather activities is from mid June to mid September.

Climate in Waltham

very coldcoldcoolwarmcoolcoldJanFebMarAprMayJunJulAugSepOctNovDecNowNow64%64%46%46%clearovercastprecipitation: 4.1 inprecipitation: 4.1 in2.8 in2.8 inmuggy: 40%muggy: 40%0%0%drydrytourism score: 6.6tourism score: 6.60.10.1
Waltham weather by month. Click on each chart for more information.

The warm season lasts for 3.4 months, from June 2 to September 14, with an average daily high temperature above 73°F. The hottest month of the year in Waltham is July, with an average high of 82°F and low of 63°F.

The cold season lasts for 3.4 months, from December 1 to March 12, with an average daily high temperature below 45°F. The coldest month of the year in Waltham is January, with an average low of 21°F and high of 36°F.

Average High and Low Temperature in Waltham

Average High and Low Temperature in WalthamwarmcoldcoldJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F10°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°F100°F100°FJan 2935°FJan 2935°FJul 2083°FJul 2083°F19°F19°F64°F64°FJun 273°FJun 273°FSep 1473°FSep 1473°FDec 145°FDec 145°FMar 1245°FMar 1245°F54°F54°F55°F55°F30°F30°F28°F28°FNowNow
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.
AverageJanFebMarAprMayJunJulAugSepOctNovDec
High 36°F38°F46°F58°F68°F77°F82°F80°F72°F61°F50°F40°F
Temp. 27°F29°F37°F48°F58°F67°F73°F71°F63°F52°F42°F33°F
Low 21°F22°F30°F40°F49°F58°F63°F62°F54°F44°F35°F26°F

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in Waltham

Average Hourly Temperature in WalthamJanFebMarAprMayJunJulAugSepOctNovDec12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMNowNowfreezingfreezingvery coldvery coldcoldcoldcoolcomfortablecomfortablewarmfreezingfreezing
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Odessa, Ukraine (4,667 miles away) and Nizhneye Kazanishche, Russia (5,428 miles) are the far-away foreign places with temperatures most similar to Waltham (view comparison).

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Compare Waltham to another city:

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In Waltham, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year in Waltham begins around June 25 and lasts for 4.3 months, ending around November 5.

The clearest month of the year in Waltham is September, during which on average the sky is clear, mostly clear, or partly cloudy 62% of the time.

The cloudier part of the year begins around November 5 and lasts for 7.7 months, ending around June 25.

The cloudiest month of the year in Waltham is March, during which on average the sky is overcast or mostly cloudy 53% of the time.

Cloud Cover Categories in Waltham

Cloud Cover Categories in WalthamclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Sep 564%Sep 564%Feb 2846%Feb 2846%Jun 2554%Jun 2554%Nov 555%Nov 555%NowNowclearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.
FractionJanFebMarAprMayJunJulAugSepOctNovDec
Cloudier 52%53%53%53%53%49%43%39%38%41%48%52%
Clearer 48%47%47%47%47%51%57%61%62%59%52%48%

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Waltham varies throughout the year.

The wetter season lasts 9.1 months, from March 18 to December 21, with a greater than 28% chance of a given day being a wet day. The month with the most wet days in Waltham is June, with an average of 9.6 days with at least 0.04 inches of precipitation.

The drier season lasts 2.9 months, from December 21 to March 18. The month with the fewest wet days in Waltham is February, with an average of 7.2 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Waltham is June, with an average of 9.6 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 34% on May 28.

Daily Chance of Precipitation in Waltham

Daily Chance of Precipitation in WalthamwetdryJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%May 2834%May 2834%Jan 2923%Jan 2923%Mar 1828%Mar 1828%Dec 2128%Dec 2128%NowNowrainmixedsnow
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).
Days ofJanFebMarAprMayJunJulAugSepOctNovDec
Rain 3.2d3.4d6.1d7.7d9.6d9.6d9.7d8.7d7.5d7.7d6.8d5.3d
Mixed 2.4d2.0d1.7d0.4d0.0d0.0d0.0d0.0d0.0d0.1d0.9d2.0d
Snow 2.1d1.8d0.8d0.1d0.0d0.0d0.0d0.0d0.0d0.0d0.2d1.4d
Any 7.8d7.2d8.6d8.2d9.6d9.6d9.7d8.7d7.5d7.9d7.9d8.7d

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Waltham experiences significant seasonal variation in monthly rainfall.

Rain falls throughout the year in Waltham. The month with the most rain in Waltham is October, with an average rainfall of 3.9 inches.

The month with the least rain in Waltham is January, with an average rainfall of 1.9 inches.

Average Monthly Rainfall in Waltham

Average Monthly Rainfall in WalthamJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in2 in2 in4 in4 in6 in6 in8 in8 in10 in10 in12 in12 inOct 143.9 inOct 143.9 inJan 241.8 inJan 241.8 inApr 23.8 inApr 23.8 inJun 13.6 inJun 13.6 inAug 93.2 inAug 93.2 inNowNow
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.
JanFebMarAprMayJunJulAugSepOctNovDec
Rainfall 1.9″2.2″3.3″3.6″3.4″3.3″2.9″3.1″3.4″3.9″3.7″2.9″

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Waltham experiences extreme seasonal variation in monthly snowfall.

The snowy period of the year lasts for 5.4 months, from November 3 to April 14, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Waltham is January, with an average snowfall of 10.9 inches.

The snowless period of the year lasts for 6.6 months, from April 14 to November 3. The least snow falls around July 27, with an average total accumulation of 0.0 inches.

Average Monthly Snowfall in Waltham

Average Monthly Snowfall in WalthamsnowsnowJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in5 in5 in10 in10 in15 in15 in20 in20 in25 in25 inJan 2711.3 inJan 2711.3 inJul 270.0 inJul 270.0 inNov 31.0 inNov 31.0 inApr 141.0 inApr 141.0 inNowNow
The average snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.
JanFebMarAprMayJunJulAugSepOctNovDec
Snowfall 10.9″10.5″5.7″0.9″0.0″0.0″0.0″0.0″0.0″0.2″2.3″7.5″

The length of the day in Waltham varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 4 minutes of daylight; the longest day is June 20, with 15 hours, 17 minutes of daylight.

Hours of Daylight and Twilight in Waltham

Hours of Daylight and Twilight in WalthamJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 8 minMar 1912 hr, 8 minMar 1915 hr, 17 minJun 2015 hr, 17 minJun 2012 hr, 11 minSep 2212 hr, 11 minSep 229 hr, 4 minDec 219 hr, 4 minDec 21nightnightdayNowNow
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.
Hours ofJanFebMarAprMayJunJulAugSepOctNovDec
Daylight 9.5h10.6h12.0h13.4h14.6h15.2h14.9h13.8h12.4h11.0h9.8h9.1h

The earliest sunrise is at 5:07 AM on June 14, and the latest sunrise is 2 hours, 13 minutes later at 7:20 AM on November 2. The earliest sunset is at 4:12 PM on December 8, and the latest sunset is 4 hours, 14 minutes later at 8:26 PM on June 27.

Daylight saving time (DST) is observed in Waltham during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

Sunrise & Sunset with Twilight and Daylight Saving Time in Waltham

Sunrise & Sunset with Twilight and Daylight Saving Time in WalthamJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 145:07 AMJun 145:07 AM8:26 PMJun 278:26 PMJun 27Dec 84:12 PMDec 84:12 PM7:20 AMNov 27:20 AMNov 2Mar 10DSTMar 10DSTDSTNov 3DSTNov 3daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2024. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

Solar Elevation and Azimuth in Waltham

Solar Elevation and Azimuth in WalthamJanFebMarAprMayJunJulAugSepOctNovDec12 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AM0001010101020202030303040405050606000010101020202020303040405050602471NowNow
northeastsouthwest
Solar elevation and azimuth over the course of the year 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

Moon Rise, Set & Phases in Waltham

The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

Waltham experiences significant seasonal variation in the perceived humidity.

The muggier period of the year lasts for 3.4 months, from June 7 to September 20, during which time the comfort level is muggy, oppressive, or miserable at least 10% of the time. The month with the most muggy days in Waltham is July, with 11.0 days that are muggy or worse.

The least muggy day of the year is February 10, when muggy conditions are essentially unheard of.

Humidity Comfort Levels in Waltham

Humidity Comfort Levels in WalthammuggyJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Feb 100%Feb 100%Jul 2940%Jul 2940%Jun 710%Jun 710%Sep 2010%Sep 2010%NowNowoppressiveoppressivemuggymuggydrydrycomfortablecomfortable
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.
JanFebMarAprMayJunJulAugSepOctNovDec
Muggy days 0.0d0.0d0.0d0.0d0.7d4.8d11.0d9.5d3.7d0.6d0.0d0.0d

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Waltham experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 5.8 months, from October 29 to April 23, with average wind speeds of more than 5.9 miles per hour. The windiest month of the year in Waltham is February, with an average hourly wind speed of 7.6 miles per hour.

The calmer time of year lasts for 6.2 months, from April 23 to October 29. The calmest month of the year in Waltham is August, with an average hourly wind speed of 4.3 miles per hour.

Average Wind Speed in Waltham

Average Wind Speed in WalthamwindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph0 mph2 mph2 mph4 mph4 mph6 mph6 mph8 mph8 mph10 mph10 mph12 mph12 mphFeb 237.7 mphFeb 237.7 mphJul 314.1 mphJul 314.1 mphOct 295.9 mphOct 295.9 mphApr 235.9 mphApr 235.9 mphNowNow
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
JanFebMarAprMayJunJulAugSepOctNovDec
Wind Speed (mph) 7.37.67.26.25.24.64.34.34.85.56.26.7

The predominant average hourly wind direction in Waltham is from the west throughout the year.

Wind Direction in Waltham

Wind Direction in WalthamJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%NowNowwestsouthnortheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Waltham is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences significant seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.0 months, from June 24 to September 25, with an average temperature above 60°F. The month of the year in Waltham with the warmest water is August, with an average temperature of 65°F.

The time of year with cooler water lasts for 3.8 months, from December 27 to April 20, with an average temperature below 44°F. The month of the year in Waltham with the coolest water is February, with an average temperature of 38°F.

Average Water Temperature in Waltham

Average Water Temperature in WalthamwarmcoolJanFebMarAprMayJunJulAugSepOctNovDec30°F30°F35°F35°F40°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°F70°F70°FAug 666°FAug 666°F38°FFeb 2838°FFeb 28Jun 2460°FJun 2460°FSep 2560°FSep 2560°FDec 2744°FDec 2744°FApr 2044°FApr 2044°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.
WaterJanFebMarAprMayJunJulAugSepOctNovDec
Temperature 41°F38°F39°F43°F50°F58°F64°F65°F62°F56°F50°F45°F

To characterize how pleasant the weather is in Waltham throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Waltham for general outdoor tourist activities is from mid June to mid September, with a peak score in the last week of August.

Tourism Score in Waltham

Tourism Score in Walthambest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.66.60.10.1NowNowtemperaturetemperature cloudscloudsprecipitationprecipitationtourism score
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Waltham for hot-weather activities is from early July to mid August, with a peak score in the last week of July.

Beach/Pool Score in Waltham

Beach/Pool Score in Walthambest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810105.45.40.00.0NowNowtemperaturetemperature cloudscloudsprecipitationprecipitationbeach/pool score
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Waltham typically lasts for 6.0 months (184 days), from around April 16 to around October 18, rarely starting before March 31 or after May 2, and rarely ending before September 29 or after November 6.

Time Spent in Various Temperature Bands and the Growing Season in Waltham

Time Spent in Various Temperature Bands and the Growing Season in Walthamgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Apr 1650%Apr 1650%Oct 1850%Oct 1890%May 290%May 290%Sep 2990%Sep 2910%Mar 3110%Mar 3110%Nov 610%Nov 60%Feb 60%Feb 6Jul 18100%Jul 18100%NowNowfrigidfreezingvery coldcoldcoolcomfortablewarmhot
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms in Waltham should appear around April 21, only rarely appearing before April 6 or after May 3.

Growing Degree Days in Waltham

Growing Degree Days in WalthamJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F500°F500°F1,000°F1,000°F1,500°F1,500°F2,000°F2,000°F2,500°F2,500°F3,000°F3,000°FApr 2189°FApr 2189°FJun 30900°FJun 30900°FAug 101,800°FAug 101,800°FDec 312,840°FDec 312,840°FNowNow
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.5 months, from May 4 to August 20, with an average daily incident shortwave energy per square meter above 5.8 kWh. The brightest month of the year in Waltham is June, with an average of 6.6 kWh.

The darker period of the year lasts for 3.3 months, from November 2 to February 11, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest month of the year in Waltham is December, with an average of 1.7 kWh.

Average Daily Incident Shortwave Solar Energy in Waltham

Average Daily Incident Shortwave Solar Energy in WalthambrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWh9 kWh9 kWhJun 296.8 kWhJun 296.8 kWhDec 231.6 kWhDec 231.6 kWhMay 45.8 kWhMay 45.8 kWhAug 205.8 kWhAug 205.8 kWhNov 22.6 kWhNov 22.6 kWhFeb 112.6 kWhFeb 112.6 kWhNowNow
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.
JanFebMarAprMayJunJulAugSepOctNovDec
Solar Energy (kWh) 1.92.84.05.26.06.66.55.84.83.42.21.7

For the purposes of this report, the geographical coordinates of Waltham are 42.376 deg latitude, -71.236 deg longitude, and 62 ft elevation.

The topography within 2 miles of Waltham contains only modest variations in elevation, with a maximum elevation change of 449 feet and an average elevation above sea level of 110 feet. Within 10 miles also contains only modest variations in elevation (430 feet). Within 50 miles contains only modest variations in elevation (2,264 feet).

The area within 2 miles of Waltham is covered by artificial surfaces (93%), within 10 miles by artificial surfaces (67%) and trees (27%), and within 50 miles by trees (48%) and artificial surfaces (26%).

This report illustrates the typical weather in Waltham, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There are 5 weather stations near enough to contribute to our estimation of the temperature and dew point in Waltham.

For each station, the records are corrected for the elevation difference between that station and Waltham according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

The estimated value at Waltham is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Waltham and a given station.

The stations contributing to this reconstruction are:

To get a sense of how much these sources agree with each other, you can view a comparison of Waltham and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 data.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © OpenStreetMap contributors.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.

Please review our full terms contained on our Terms of Service page.