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Climate and Average Weather Year Round in Great Falls Virginia, United States

In Great Falls, the summers are warm and humid, the winters are very cold and snowy, and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 26°F to 87°F and is rarely below 13°F or above 95°F.

Based on the tourism score, the best times of year to visit Great Falls for warm-weather activities are from early June to early July and from early August to late September.

Climate in Great Falls

very coldcoldcoolwarmhotwarmcoolcoldJanFebMarAprMayJunJulAugSepOctNovDecNowNow65%65%48%48%clearovercastprecipitation: 3.6 inprecipitation: 3.6 in2.4 in2.4 inmuggy: 64%muggy: 64%0%0%drydrytourism score: 6.5tourism score: 6.50.30.3
Great Falls weather by month. Click on each chart for more information.

The hot season lasts for 3.6 months, from May 30 to September 16, with an average daily high temperature above 78°F. The hottest month of the year in Great Falls is July, with an average high of 87°F and low of 68°F.

The cold season lasts for 3.1 months, from December 1 to March 3, with an average daily high temperature below 51°F. The coldest month of the year in Great Falls is January, with an average low of 27°F and high of 42°F.

Average High and Low Temperature in Great Falls

Average High and Low Temperature in Great FallshotcoldcoldJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F10°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°F100°F100°FJan 3042°FJan 3042°FJul 2187°FJul 2187°F26°F26°F69°F69°FMay 3078°FMay 3078°FSep 1678°FSep 1678°FDec 151°FDec 151°FMar 351°FMar 351°F58°F58°F60°F60°F35°F35°F33°F33°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 42°F46°F55°F66°F75°F83°F87°F85°F78°F67°F56°F46°F
Temp. 34°F36°F45°F55°F64°F73°F77°F75°F68°F56°F47°F38°F
Low 27°F29°F36°F45°F55°F63°F68°F66°F59°F48°F38°F31°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 Great Falls

Average Hourly Temperature in Great FallsJanFebMarAprMayJunJulAugSepOctNovDec12 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 AMNowNowfreezingvery coldvery coldcoldcoldcoolcoolcomfortablewarmhotfreezingvery cold
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.

Tbilisi, Georgia (5,788 miles away) is the far-away foreign place with temperatures most similar to Great Falls (view comparison).

Map
Marker
© Esri, et al.

Compare Great Falls to another city:

Map

In Great Falls, 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 Great Falls begins around July 2 and lasts for 4.3 months, ending around November 12.

The clearest month of the year in Great Falls is September, during which on average the sky is clear, mostly clear, or partly cloudy 64% of the time.

The cloudier part of the year begins around November 12 and lasts for 7.7 months, ending around July 2.

The cloudiest month of the year in Great Falls is January, during which on average the sky is overcast or mostly cloudy 52% of the time.

Cloud Cover Categories in Great Falls

Cloud Cover Categories in Great FallsclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Sep 2365%Sep 2365%Jan 1148%Jan 1148%Jul 256%Jul 256%Nov 1257%Nov 1257%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%51%50%48%48%45%41%37%36%37%44%51%
Clearer 48%49%50%52%52%55%59%63%64%63%56%49%

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

The wetter season lasts 4.5 months, from April 9 to August 25, with a greater than 30% chance of a given day being a wet day. The month with the most wet days in Great Falls is June, with an average of 11.4 days with at least 0.04 inches of precipitation.

The drier season lasts 7.5 months, from August 25 to April 9. The month with the fewest wet days in Great Falls is January, with an average of 6.5 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 Great Falls is June, with an average of 11.4 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 39% on June 17.

Daily Chance of Precipitation in Great Falls

Daily Chance of Precipitation in Great FallswetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Jun 1739%Jun 1739%Oct 2020%Oct 2020%Jan 121%Jan 121%Apr 930%Apr 930%Aug 2530%Aug 2530%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 4.1d4.1d7.1d8.9d10.9d11.4d11.4d10.0d7.9d6.8d6.3d5.6d
Mixed 1.1d0.9d0.4d0.0d0.0d0.0d0.0d0.0d0.0d0.0d0.1d0.5d
Snow 1.3d1.3d0.6d0.0d0.0d0.0d0.0d0.0d0.0d0.0d0.4d0.9d
Any 6.5d6.4d8.1d9.0d10.9d11.4d11.4d10.0d7.9d6.8d6.8d7.0d

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. Great Falls experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year in Great Falls. The month with the most rain in Great Falls is May, with an average rainfall of 3.6 inches.

The month with the least rain in Great Falls is January, with an average rainfall of 1.8 inches.

Average Monthly Rainfall in Great Falls

Average Monthly Rainfall in Great FallsJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in2 in2 in4 in4 in6 in6 in8 in8 inMay 203.6 inMay 203.6 inJan 291.8 inJan 291.8 inSep 293.4 inSep 293.4 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 1.8″1.9″2.8″3.3″3.6″3.4″3.1″3.0″3.3″3.2″3.0″2.6″

Snowfall

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

The snowy period of the year lasts for 4.3 months, from November 19 to March 27, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Great Falls is February, with an average snowfall of 6.9 inches.

The snowless period of the year lasts for 7.7 months, from March 27 to November 19. The least snow falls around July 14, with an average total accumulation of 0.0 inches.

Average Monthly Snowfall in Great Falls

Average Monthly Snowfall in Great FallssnowsnowJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in5 in5 in10 in10 in15 in15 in20 in20 inFeb 57.2 inFeb 57.2 inJul 140.0 inJul 140.0 inNov 191.0 inNov 191.0 inMar 271.0 inMar 271.0 in
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 6.3″6.9″2.3″0.0″0.0″0.0″0.0″0.0″0.0″0.0″0.7″3.6″

The length of the day in Great Falls varies significantly over the course of the year. In 2021, the shortest day is December 21, with 9 hours, 26 minutes of daylight; the longest day is June 20, with 14 hours, 55 minutes of daylight.

Hours of Daylight and Twilight in Great Falls

Hours of Daylight and Twilight in Great FallsJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 7 minMar 2012 hr, 7 minMar 2014 hr, 55 minJun 2014 hr, 55 minJun 2012 hr, 9 minSep 2212 hr, 9 minSep 229 hr, 26 minDec 219 hr, 26 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 9.8h10.8h12.0h13.3h14.4h14.9h14.6h13.6h12.4h11.1h10.0h9.5h

The earliest sunrise is at 5:42 AM on June 13, and the latest sunrise is 1 hour, 59 minutes later at 7:42 AM on November 6. The earliest sunset is at 4:46 PM on December 7, and the latest sunset is 3 hours, 52 minutes later at 8:38 PM on June 28.

Daylight saving time (DST) is observed in Great Falls during 2021, starting in the spring on March 14, lasting 7.8 months, and ending in the fall on November 7.

Sunrise & Sunset with Twilight and Daylight Saving Time in Great Falls

Sunrise & Sunset with Twilight and Daylight Saving Time in Great FallsJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 135:42 AMJun 135:42 AM8:38 PMJun 288:38 PMJun 28Dec 74:46 PMDec 74:46 PM7:42 AMNov 67:42 AMNov 6Mar 14DSTMar 14DSTDSTNov 7DSTNov 7daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2021. 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 key lunar data for 2021. 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 Great Falls

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.

Great Falls experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 4.0 months, from May 24 to September 25, during which time the comfort level is muggy, oppressive, or miserable at least 16% of the time. The month with the most muggy days in Great Falls is July, with 18.6 days that are muggy or worse.

The month with the fewest muggy days in Great Falls is February, with 0.0 days that are muggy or worse.

Humidity Comfort Levels in Great Falls

Humidity Comfort Levels in Great FallsmuggyJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Feb 190%Feb 190%Jul 2864%Jul 2864%May 2416%May 2416%Sep 2516%Sep 2516%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 0.0d0.0d0.0d0.2d3.5d11.9d18.6d16.1d7.4d1.4d0.1d0.0d

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 Great Falls experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.5 months, from October 26 to May 9, with average wind speeds of more than 7.8 miles per hour. The windiest month of the year in Great Falls is March, with an average hourly wind speed of 9.6 miles per hour.

The calmer time of year lasts for 5.5 months, from May 9 to October 26. The calmest month of the year in Great Falls is July, with an average hourly wind speed of 6.1 miles per hour.

Average Wind Speed in Great Falls

Average Wind Speed in Great FallswindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph0 mph2 mph2 mph4 mph4 mph6 mph6 mph8 mph8 mph10 mph10 mph12 mph12 mph14 mph14 mph16 mph16 mphFeb 269.8 mphFeb 269.8 mphAug 15.9 mphAug 15.9 mphOct 267.8 mphOct 267.8 mphMay 97.8 mphMay 97.8 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) 9.19.59.68.97.66.66.16.16.97.78.38.6

The predominant average hourly wind direction in Great Falls varies throughout the year.

The wind is most often from the south for 1.2 months, from May 7 to June 13 and for 2.4 months, from July 27 to October 7, with a peak percentage of 34% on August 16. The wind is most often from the west for 1.5 months, from June 13 to July 27 and for 7.0 months, from October 7 to May 7, with a peak percentage of 37% on July 6.

Wind Direction in Great Falls

Wind Direction in Great FallsWSWSWJanFebMarAprMayJunJulAugSepOctNovDec0%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).

Great Falls 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 extreme seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.3 months, from June 23 to October 2, with an average temperature above 69°F. The month of the year in Great Falls with the warmest water is August, with an average temperature of 76°F.

The time of year with cooler water lasts for 3.5 months, from December 21 to April 5, with an average temperature below 44°F. The month of the year in Great Falls with the coolest water is February, with an average temperature of 36°F.

Average Water Temperature in Great Falls

Average Water Temperature in Great FallswarmcoolJanFebMarAprMayJunJulAugSepOctNovDec30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°FAug 1077°FAug 1077°F36°FFeb 636°FFeb 6Jun 2369°FJun 2369°FOct 269°FOct 269°FDec 2144°FDec 2144°FApr 544°FApr 544°FNowNow
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.
WaterJanFebMarAprMayJunJulAugSepOctNovDec
Temperature 38°F36°F40°F47°F56°F66°F74°F76°F72°F64°F54°F45°F

To characterize how pleasant the weather is in Great Falls 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 times of year to visit Great Falls for general outdoor tourist activities are from early June to early July and from early August to late September, with a peak score in the first week of September.

Tourism Score in Great Falls

Tourism Score in Great Fallsbest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.56.50.30.36.06.05.75.7NowNowprecipitationprecipitationcloudscloudstemperaturetemperature tourism 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 Great Falls for hot-weather activities is from late June to early September, with a peak score in the last week of July.

Beach/Pool Score in Great Falls

Beach/Pool Score in Great Fallsbest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.06.00.00.0NowNowprecipitationprecipitationcloudscloudstemperaturetemperature beach/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 Great Falls typically lasts for 6.8 months (210 days), from around April 4 to around October 30, rarely starting before March 17 or after April 21, and rarely ending before October 12 or after November 16.

Time Spent in Various Temperature Bands and the Growing Season in Great Falls

Time Spent in Various Temperature Bands and the Growing Season in Great Fallsgrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Apr 450%Apr 450%Oct 3050%Oct 3090%Apr 2190%Apr 2190%Oct 1290%Oct 1210%Mar 1710%Mar 1710%Nov 1610%Nov 160%Dec 150%Dec 15Jul 15100%Jul 15100%freezingvery coldcoldcoolcomfortablewarmhotfrigid
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 Great Falls should appear around March 22, only rarely appearing before March 6 or after April 7.

Growing Degree Days in Great Falls

Growing Degree Days in Great FallsJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F500°F500°F1,000°F1,000°F1,500°F1,500°F2,000°F2,000°F2,500°F2,500°F3,000°F3,000°F3,500°F3,500°F4,000°F4,000°FMar 2286°FMar 2286°FJun 5900°FJun 5900°FJul 131,800°FJul 131,800°FDec 313,964°FDec 313,964°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 significant seasonal variation over the course of the year.

The brighter period of the year lasts for 3.8 months, from April 28 to August 23, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest month of the year in Great Falls is June, with an average of 6.8 kWh.

The darker period of the year lasts for 3.1 months, from November 6 to February 9, with an average daily incident shortwave energy per square meter below 3.0 kWh. The darkest month of the year in Great Falls is December, with an average of 2.1 kWh.

Average Daily Incident Shortwave Solar Energy in Great Falls

Average Daily Incident Shortwave Solar Energy in Great FallsbrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWh9 kWh9 kWhJun 236.9 kWhJun 236.9 kWhDec 242.0 kWhDec 242.0 kWhApr 285.9 kWhApr 285.9 kWhAug 235.9 kWhAug 235.9 kWhNov 63.0 kWhNov 63.0 kWhFeb 93.0 kWhFeb 93.0 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) 2.33.24.45.56.46.86.76.15.13.82.62.1

For the purposes of this report, the geographical coordinates of Great Falls are 38.998 deg latitude, -77.288 deg longitude, and 338 ft elevation.

The topography within 2 miles of Great Falls contains only modest variations in elevation, with a maximum elevation change of 276 feet and an average elevation above sea level of 308 feet. Within 10 miles contains only modest variations in elevation (499 feet). Within 50 miles contains significant variations in elevation (2,897 feet).

The area within 2 miles of Great Falls is covered by trees (92%), within 10 miles by artificial surfaces (53%) and trees (36%), and within 50 miles by trees (42%) and cropland (31%).

This report illustrates the typical weather in Great Falls, 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 Great Falls.

For each station, the records are corrected for the elevation difference between that station and Great Falls 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 Great Falls is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Great Falls 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 Great Falls 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 © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.

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.