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Climate and Average Weather Year Round in Philadelphia Pennsylvania, United States

In Philadelphia, the summers are warm, humid, and wet; 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 94°F.

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

Climate in Philadelphia

very coldcoldcoolwarmhotwarmcoolcoldJanFebMarAprMayJunJulAugSepOctNovDecNowNow64%64%46%46%clearovercastprecipitation: 3.8 inprecipitation: 3.8 in2.7 in2.7 inmuggy: 58%muggy: 58%0%0%drydrytourism score: 6.7tourism score: 6.70.20.2
Philadelphia 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 77°F. The hottest month of the year in Philadelphia is July, with an average high of 86°F and low of 69°F.

The cold season lasts for 3.1 months, from December 2 to March 7, with an average daily high temperature below 49°F. The coldest month of the year in Philadelphia is January, with an average low of 27°F and high of 41°F.

Average High and Low Temperature in Philadelphia

Average High and Low Temperature in PhiladelphiahotcoldcoldJanFebMarAprMayJunJulAugSepOctNovDec0°F0°F10°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°F100°F100°FJan 3040°FJan 3040°FJul 2187°FJul 2187°F26°F26°F70°F70°FMay 3077°FMay 3077°FSep 1677°FSep 1677°FDec 249°FDec 249°FMar 749°FMar 749°F59°F59°F61°F61°F36°F36°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 41°F44°F53°F64°F74°F82°F86°F84°F77°F66°F55°F45°F
Temp. 33°F35°F43°F54°F64°F73°F78°F76°F69°F57°F47°F38°F
Low 27°F29°F36°F45°F55°F64°F69°F68°F60°F49°F40°F32°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 Philadelphia

Average Hourly Temperature in PhiladelphiaJanFebMarAprMayJunJulAugSepOctNovDec12 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 coldcoldcoldcoolcoolcomfortablewarmhotfreezing
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 (5,665 miles away) is the far-away foreign place with temperatures most similar to Philadelphia (view comparison).

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Marker
© Esri, et al.

Compare Philadelphia to another city:

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In Philadelphia, 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 Philadelphia begins around June 25 and lasts for 4.6 months, ending around November 13.

The clearest month of the year in Philadelphia is September, during which on average the sky is clear, mostly clear, or partly cloudy 63% of the time.

The cloudier part of the year begins around November 13 and lasts for 7.4 months, ending around June 25.

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

Cloud Cover Categories in Philadelphia

Cloud Cover Categories in PhiladelphiaclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Sep 2364%Sep 2364%Jan 346%Jan 346%Jun 2555%Jun 2555%Nov 1356%Nov 1356%NowNowclearmostly clearmostly cloudyovercastpartly cloudy
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 53%52%51%49%49%47%41%38%37%38%45%52%
Clearer 47%48%49%51%51%53%59%62%63%62%55%48%

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

The wetter season lasts 4.9 months, from March 31 to August 27, with a greater than 29% chance of a given day being a wet day. The month with the most wet days in Philadelphia is July, with an average of 11.1 days with at least 0.04 inches of precipitation.

The drier season lasts 7.1 months, from August 27 to March 31. The month with the fewest wet days in Philadelphia is January, with an average of 7.0 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 Philadelphia is July, with an average of 11.1 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 37% on July 29.

Daily Chance of Precipitation in Philadelphia

Daily Chance of Precipitation in PhiladelphiawetdrydryJanFebMarAprMayJunJulAugSepOctNovDec0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%Jul 2937%Jul 2937%Jan 2822%Jan 2822%Jan 123%Jan 123%Mar 3129%Mar 3129%NowNowrainmixed
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 4.6d4.4d7.2d8.8d10.0d10.5d11.1d10.1d8.2d7.5d7.3d6.2d
Mixed 1.2d1.0d0.3d0.0d0.0d0.0d0.0d0.0d0.0d0.0d0.1d0.5d
Snow 1.3d1.3d0.9d0.1d0.0d0.0d0.0d0.0d0.0d0.0d0.2d1.0d
Any 7.0d6.8d8.4d8.9d10.0d10.5d11.1d10.1d8.2d7.5d7.6d7.7d

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. Philadelphia experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year in Philadelphia. The month with the most rain in Philadelphia is July, with an average rainfall of 3.7 inches.

The month with the least rain in Philadelphia is February, with an average rainfall of 2.2 inches.

Average Monthly Rainfall in Philadelphia

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 2.2″2.2″3.2″3.6″3.3″3.5″3.7″3.6″3.5″3.4″3.2″3.1″

Snowfall

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

The snowy period of the year lasts for 4.2 months, from November 22 to March 28, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Philadelphia is January, with an average snowfall of 6.0 inches.

The snowless period of the year lasts for 7.8 months, from March 28 to November 22. The least snow falls around August 1, with an average total accumulation of 0.0 inches.

Average Monthly Snowfall in Philadelphia

Average Monthly Snowfall in PhiladelphiasnowsnowJanFebMarAprMayJunJulAugSepOctNovDec0 in0 in5 in5 in10 in10 in15 in15 in20 in20 inJan 256.5 inJan 256.5 inAug 10.0 inAug 10.0 inNov 221.0 inNov 221.0 inMar 281.0 inMar 281.0 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 6.0″6.0″2.3″0.1″0.0″0.0″0.0″0.0″0.0″0.0″0.5″3.1″

The length of the day in Philadelphia varies significantly over the course of the year. In 2022, the shortest day is December 21, with 9 hours, 20 minutes of daylight; the longest day is June 21, with 15 hours, 1 minute of daylight.

Hours of Daylight and Twilight in Philadelphia

Hours of Daylight and Twilight in PhiladelphiaJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 6 minMar 2012 hr, 6 minMar 2015 hr, 1 minJun 2115 hr, 1 minJun 2112 hr, 9 minSep 2212 hr, 9 minSep 229 hr, 20 minDec 219 hr, 20 minDec 21nightnightday
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 9.7h10.7h12.0h13.3h14.4h15.0h14.7h13.7h12.4h11.1h10.0h9.4h

The earliest sunrise is at 5:31 AM on June 14, and the latest sunrise is 2 hours, 3 minutes later at 7:34 AM on November 5. The earliest sunset is at 4:35 PM on December 7, and the latest sunset is 3 hours, 58 minutes later at 8:33 PM on June 28.

Daylight saving time (DST) is observed in Philadelphia during 2022, starting in the spring on March 13, lasting 7.8 months, and ending in the fall on November 6.

Sunrise & Sunset with Twilight and Daylight Saving Time in Philadelphia

Sunrise & Sunset with Twilight and Daylight Saving Time in PhiladelphiaJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 145:31 AMJun 145:31 AM8:33 PMJun 288:33 PMJun 28Dec 74:35 PMDec 74:35 PM7:34 AMNov 57:34 AMNov 5Mar 13DSTMar 13DSTDSTNov 6DSTNov 6daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunsetNowNow
The solar day over the course of the year 2022. 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 2022. 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 Philadelphia

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.

Philadelphia experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 4.0 months, from May 29 to September 27, during which time the comfort level is muggy, oppressive, or miserable at least 14% of the time. The month with the most muggy days in Philadelphia is July, with 16.6 days that are muggy or worse.

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

Humidity Comfort Levels in Philadelphia

Humidity Comfort Levels in PhiladelphiamuggyJanFebMarAprMayJunJulAugSepOctNovDec0%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 2958%Jul 2958%May 2914%May 2914%Sep 2714%Sep 2714%NowNowoppressiveoppressivemuggymuggydrydryhumidhumidcomfortablecomfortable
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 0.0d0.0d0.0d0.1d2.3d9.3d16.6d14.5d7.0d1.4d0.1d0.0d

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 Philadelphia experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.4 months, from October 28 to May 9, with average wind speeds of more than 7.4 miles per hour. The windiest month of the year in Philadelphia is March, with an average hourly wind speed of 9.0 miles per hour.

The calmer time of year lasts for 5.6 months, from May 9 to October 28. The calmest month of the year in Philadelphia is August, with an average hourly wind speed of 5.7 miles per hour.

Average Wind Speed in Philadelphia

Average Wind Speed in PhiladelphiawindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph0 mph2 mph2 mph4 mph4 mph6 mph6 mph8 mph8 mph10 mph10 mph12 mph12 mph14 mph14 mphFeb 269.2 mphFeb 269.2 mphAug 135.5 mphAug 135.5 mphOct 287.4 mphOct 287.4 mphMay 97.4 mphMay 97.4 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) 8.58.99.08.47.16.25.85.76.37.17.78.0

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

The wind is most often from the south for 2.3 months, from July 21 to September 29, with a peak percentage of 36% on August 2. The wind is most often from the west for 9.7 months, from September 29 to July 21, with a peak percentage of 45% on January 1.

Wind Direction in Philadelphia

Wind Direction in PhiladelphiaWSWJanFebMarAprMayJunJulAugSepOctNovDec0%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).

Philadelphia 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 3.5 months, from June 20 to October 3, with an average temperature above 67°F. The month of the year in Philadelphia with the warmest water is August, with an average temperature of 74°F.

The time of year with cooler water lasts for 3.6 months, from December 22 to April 8, with an average temperature below 46°F. The month of the year in Philadelphia with the coolest water is February, with an average temperature of 39°F.

Average Water Temperature in Philadelphia

Average Water Temperature in PhiladelphiawarmcoolJanFebMarAprMayJunJulAugSepOctNovDec30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°FAug 774°FAug 774°F39°FFeb 1939°FFeb 19Jun 2067°FJun 2067°FOct 367°FOct 367°FDec 2246°FDec 2246°FApr 846°FApr 846°FNowNow
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.
WaterJanFebMarAprMayJunJulAugSepOctNovDec
Temperature 42°F39°F42°F48°F56°F66°F73°F74°F71°F63°F55°F47°F

To characterize how pleasant the weather is in Philadelphia 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 Philadelphia 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 Philadelphia

Tourism Score in Philadelphiabest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.76.70.20.26.16.15.85.8NowNowprecipitationprecipitationcloudscloudstemperaturetemperature 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 Philadelphia 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 Philadelphia

Beach/Pool Score in Philadelphiabest timeJanFebMarAprMayJunJulAugSepOctNovDec002244668810106.26.20.00.0NowNowprecipitationprecipitationcloudscloudstemperaturetemperature 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 Philadelphia typically lasts for 7.2 months (222 days), from around April 2 to around November 10, rarely starting before March 16 or after April 18, and rarely ending before October 24 or after November 26.

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

Time Spent in Various Temperature Bands and the Growing Season in Philadelphiagrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Apr 250%Apr 250%Nov 1050%Nov 1090%Apr 1890%Apr 1890%Oct 2490%Oct 2410%Mar 1610%Mar 1610%Nov 2610%Nov 26Jul 18100%Jul 18100%NowNowfreezingvery 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 Philadelphia should appear around March 29, only rarely appearing before March 13 or after April 13.

Growing Degree Days in Philadelphia

Growing Degree Days in PhiladelphiaJanFebMarAprMayJunJulAugSepOctNovDec0°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 2985°FMar 2985°FJun 9900°FJun 9900°FJul 161,800°FJul 161,800°FDec 313,913°FDec 313,913°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 3.8 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 Philadelphia 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 2.8 kWh. The darkest month of the year in Philadelphia is December, with an average of 1.9 kWh.

Average Daily Incident Shortwave Solar Energy in Philadelphia

Average Daily Incident Shortwave Solar Energy in PhiladelphiabrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWh9 kWh9 kWhJun 296.9 kWhJun 296.9 kWhDec 231.8 kWhDec 231.8 kWhApr 285.9 kWhApr 285.9 kWhAug 235.9 kWhAug 235.9 kWhFeb 92.8 kWhFeb 92.8 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) 2.23.04.25.46.36.86.66.05.03.72.51.9

For the purposes of this report, the geographical coordinates of Philadelphia are 39.952 deg latitude, -75.164 deg longitude, and 39 ft elevation.

The topography within 2 miles of Philadelphia contains only modest variations in elevation, with a maximum elevation change of 105 feet and an average elevation above sea level of 37 feet. Within 10 miles also contains only modest variations in elevation (443 feet). Within 50 miles contains only modest variations in elevation (1,250 feet).

The area within 2 miles of Philadelphia is covered by artificial surfaces (92%), within 10 miles by artificial surfaces (90%), and within 50 miles by trees (41%) and artificial surfaces (27%).

This report illustrates the typical weather in Philadelphia, 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Philadelphia.

For each station, the records are corrected for the elevation difference between that station and Philadelphia 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 Philadelphia is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Philadelphia 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 Philadelphia 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.