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Fall Weather in Philadelphia Pennsylvania, United States

Daily high temperatures decrease by 31°F, from 82°F to 50°F, rarely falling below 38°F or exceeding 89°F.

Daily low temperatures decrease by 29°F, from 65°F to 36°F, rarely falling below 25°F or exceeding 72°F.

For reference, on July 21, the hottest day of the year, temperatures in Philadelphia typically range from 70°F to 87°F, while on January 30, the coldest day of the year, they range from 26°F to 40°F.

Average High and Low Temperature in the Fall in Philadelphia

Average High and Low Temperature in the Fall in PhiladelphiaSepOctNov20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°FSummerWinterSep 182°FSep 182°F65°F65°FNov 3050°FNov 3050°F36°F36°FOct 172°FOct 172°F55°F55°FNov 161°FNov 161°F44°F44°F
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.

The figure below shows you a compact characterization of the hourly average fall temperatures. The horizontal axis is the day, 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 the Fall in Philadelphia

Average Hourly Temperature in the Fall in PhiladelphiaSepOctNov12 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 AMSummerWintervery coldcoldcoolcomfortablewarm
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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The fall in Philadelphia experiences rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 36% to 49%. The lowest chance of overcast or mostly cloudy conditions is 36% on September 23.

The clearest day of the fall is September 23, with clear, mostly clear, or partly cloudy conditions 64% of the time.

For reference, on January 3, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 54%, while on September 23, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 64%.

Cloud Cover Categories in the Fall in Philadelphia

Cloud Cover Categories in the Fall in PhiladelphiaSepOctNov0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%SummerWinterJan 346%Jan 346%Sep 164%Sep 164%Nov 3051%Nov 3051%Oct 163%Oct 163%Nov 158%Nov 158%clearmostly clearpartly 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.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Philadelphia, the chance of a wet day over the course of the fall is essentially constant, remaining around 25% throughout.

For reference, the year's highest daily chance of a wet day is 37% on July 29, and its lowest chance is 22% on January 28.

Over the course of the fall in Philadelphia, the chance of a day with only rain decreases from 28% to 24%, the chance of a day with mixed snow and rain increases from 0% to 2%, and the chance of a day with only snow remains an essentially constant 0% throughout.

Probability of Precipitation in the Fall in Philadelphia

Probability of Precipitation in the Fall in PhiladelphiaSepOctNov0%0%5%5%10%10%15%15%20%20%25%25%30%30%35%35%40%40%SummerWinterOct 2022%Oct 2022%Sep 128%Sep 128%Nov 3027%Nov 3027%Oct 127%Oct 127%rainmixedsnow
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).

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the fall in Philadelphia is essentially constant, remaining about 3.4 inches throughout, and rarely exceeding 6.3 inches or falling below 1.0 inches.

Average Monthly Rainfall in the Fall in Philadelphia

Average Monthly Rainfall in the Fall in PhiladelphiaSepOctNov0 in0 in1 in1 in2 in2 in3 in3 in4 in4 in5 in5 in6 in6 in7 in7 inSummerWinterSep 13.4 inSep 13.4 inNov 303.4 inNov 303.4 inOct 13.6 inOct 13.6 inNov 13.1 inNov 13.1 in
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.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during the fall in Philadelphia is increasing, starting the season at 0.0 inches, when it rarely exceeds -0.0 inches or falls below -0.0 inches, and ending the season at 1.6 inches, when it rarely exceeds 6.4 inches or falls below -0.0 inches.

Average Monthly Snowfall in the Fall in Philadelphia

Average Monthly Snowfall in the Fall in PhiladelphiaSepOctNov0 in0 in2 in2 in4 in4 in6 in6 in8 in8 in10 in10 in12 in12 inSummerWinterSep 10.0 inSep 10.0 inNov 301.6 inNov 301.6 inOct 10.0 inOct 10.0 inNov 10.1 inNov 10.1 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.

Over the course of the fall in Philadelphia, the length of the day is very rapidly decreasing. From the start to the end of the season, the length of the day decreases by 3 hours, 30 minutes, implying an average daily decrease of 2 minutes, 20 seconds, and weekly decrease of 16 minutes, 18 seconds.

The shortest day of the fall is November 30, with 9 hours, 34 minutes of daylight and the longest day is September 1, with 13 hours, 4 minutes of daylight.

Hours of Daylight and Twilight in the Fall in Philadelphia

Hours of Daylight and Twilight in the Fall in PhiladelphiaSepOctNov0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrSummerWinterSep 2312 hr, 10 minSep 2312 hr, 10 minnightnightdaydayNov 309 hr, 34 minNov 309 hr, 34 minNov 110 hr, 29 minNov 110 hr, 29 min
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.

The earliest sunrise of the fall in Philadelphia is 6:28 AM on September 1 and the latest sunrise is 1 hour, 5 minutes later at 7:32 AM on November 4.

The latest sunset is 7:32 PM on September 1 and the earliest sunset is 2 hours, 56 minutes earlier at 4:36 PM on November 30.

Daylight saving time (DST) ends at 1:00 AM on November 5, 2023, shifting sunrise and sunset to be an hour earlier.

For reference, on June 21, the longest day of the year, the Sun rises at 5:32 AM and sets 15 hours, 1 minute later, at 8:32 PM, while on December 22, the shortest day of the year, it rises at 7:19 AM and sets 9 hours, 20 minutes later, at 4:39 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in the Fall in Philadelphia

Sunrise & Sunset with Twilight and Daylight Saving Time in the Fall in PhiladelphiaSepOctNov12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMSummerWinter6:28 AM6:28 AMSep 17:32 PMSep 17:32 PM7:01 AM7:01 AMNov 304:36 PMNov 304:36 PM7:32 AM7:32 AMNov 45:55 PMNov 45:55 PM6:56 AM6:56 AMOct 16:43 PMOct 16:43 PMDSTNov 5DSTNov 5SolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day in the fall. 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 the Fall in Philadelphia

Solar Elevation and Azimuth in the Fall in PhiladelphiaSepOctNov12 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 AMSummerWinter0102020304050600010203040
northeastsouthwest
Solar elevation and azimuth in the the fall of 2023. 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 the fall of 2023. 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. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in the Fall in Philadelphia

Moon Rise, Set & Phases in the Fall in PhiladelphiaSepOctNov12 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMSummerWinterAug 12:32 PMAug 12:32 PMAug 165:39 AMAug 165:39 AMAug 309:36 PMAug 309:36 PMSep 149:40 PMSep 149:40 PMSep 295:58 AMSep 295:58 AMOct 141:56 PMOct 141:56 PMOct 284:25 PMOct 284:25 PMNov 134:28 AMNov 134:28 AMNov 274:17 AMNov 274:17 AMDec 126:33 PMDec 126:33 PMDec 267:34 PMDec 267:34 PM8:44 PM8:44 PM6:43 AM6:43 AM7:47 PM7:47 PM6:54 AM6:54 AM6:39 PM6:39 PM6:59 AM6:59 AM6:24 PM6:24 PM5:56 PM5:56 PM3:57 PM3:57 PM7:23 AM7:23 AM4:05 PM4:05 PM
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.

The chance that a given day will be muggy in Philadelphia is very rapidly decreasing during the fall, falling from 36% to 0% over the course of the season.

For reference, on July 29, the muggiest day of the year, there are muggy conditions 58% of the time, while on January 24, the least muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in the Fall in Philadelphia

Humidity Comfort Levels in the Fall in PhiladelphiaSepOctNov0%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%SummerWinterSep 136%Sep 136%Nov 300%Nov 300%Oct 111%Oct 111%Nov 11%Nov 11%oppressiveoppressivemuggymuggyhumidhumiddrydrycomfortablecomfortable
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.

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 is increasing during the fall, increasing from 5.9 miles per hour to 7.8 miles per hour over the course of the season.

For reference, on February 26, the windiest day of the year, the daily average wind speed is 9.2 miles per hour, while on August 13, the calmest day of the year, the daily average wind speed is 5.5 miles per hour.

Average Wind Speed in the Fall in Philadelphia

Average Wind Speed in the Fall in PhiladelphiaSepOctNov0 mph0 mph2 mph2 mph4 mph4 mph6 mph6 mph8 mph8 mph10 mph10 mph12 mph12 mph14 mph14 mphSummerWinterSep 15.9 mphSep 15.9 mphNov 307.8 mphNov 307.8 mphOct 16.7 mphOct 16.7 mphNov 17.5 mphNov 17.5 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The wind direction in Philadelphia during the fall is predominantly out of the south from September 1 to September 29 and the west from September 29 to November 30.

Wind Direction in the Fall in Philadelphia

Wind Direction in the Fall in PhiladelphiaSWSepOctNov0%100%20%80%40%60%60%40%80%20%100%0%SummerWinterwestsouthnortheast
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 surface water temperature in Philadelphia is very rapidly decreasing during the fall, falling by 22°F, from 73°F to 51°F, over the course of the season.

Average Water Temperature in the Fall in Philadelphia

Average Water Temperature in the Fall in PhiladelphiaSepOctNov35°F35°F40°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°F70°F70°F75°F75°F80°F80°FSummerWinterSep 173°FSep 173°FNov 3051°FNov 3051°FOct 168°FOct 168°FNov 159°FNov 159°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

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.

During the fall in Philadelphia, the chance that a given day is within the growing season is very rapidly decreasing falling from 100% to 6% over the course of the season.

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

Time Spent in Various Temperature Bands and the Growing Season in the Fall in Philadelphiagrowing seasonSepOctNov0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%SummerWinter100%Sep 1100%Sep 1Nov 306%Nov 306%100%Oct 1100%Oct 173%Nov 173%Nov 1very coldcoldcoolcomfortablewarmhotfreezing
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.

The average accumulated growing degree days in Philadelphia are rapidly increasing during the fall, increasing by 878°F, from 3,010°F to 3,888°F, over the course of the season.

Growing Degree Days in the Fall in Philadelphia

Growing Degree Days in the Fall in PhiladelphiaSepOctNov2,800°F2,800°F3,000°F3,000°F3,200°F3,200°F3,400°F3,400°F3,600°F3,600°F3,800°F3,800°F4,000°F4,000°F4,200°F4,200°FSummerWinterSep 13,010°FSep 13,010°FNov 303,888°FNov 303,888°FOct 13,548°FOct 13,548°FNov 13,805°FNov 13,805°F
The average growing degree days accumulated over the course of the fall, 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 in Philadelphia is very rapidly decreasing during the fall, falling by 3.5 kWh, from 5.6 kWh to 2.1 kWh, over the course of the season.

Average Daily Incident Shortwave Solar Energy in the Fall in Philadelphia

Average Daily Incident Shortwave Solar Energy in the Fall in PhiladelphiaSepOctNov0 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWhSummerWinterSep 15.6 kWhSep 15.6 kWhNov 302.1 kWhNov 302.1 kWhOct 14.4 kWhOct 14.4 kWhNov 13.0 kWhNov 13.0 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

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 © 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.

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