August Weather in Philadelphia Pennsylvania, United States
Daily high temperatures decrease by 4°F, from 86°F to 82°F, rarely falling below 74°F or exceeding 94°F.
Daily low temperatures decrease by 4°F, from 70°F to 65°F, rarely falling below 57°F or exceeding 75°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.
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on August. 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.
Tbilisi, Georgia (5,665 miles away) is the far-away foreign place with temperatures most similar to Philadelphia (view comparison).
The month of August in Philadelphia experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 38% throughout the month.
The clearest day of the month is August 31, 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%.
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 August is very rapidly decreasing, starting the month at 36% and ending it at 28%.
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.
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during August in Philadelphia is gradually decreasing, starting the month at 3.8 inches, when it rarely exceeds 5.8 inches or falls below 1.6 inches, and ending the month at 3.4 inches, when it rarely exceeds 5.6 inches or falls below 1.4 inches.
The lowest average 31-day accumulation is 3.4 inches on August 31.
Over the course of August in Philadelphia, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 9 minutes, implying an average daily decrease of 2 minutes, 18 seconds, and weekly decrease of 16 minutes, 4 seconds.
The shortest day of the month is August 31, with 13 hours, 7 minutes of daylight and the longest day is August 1, with 14 hours, 15 minutes of daylight.
The earliest sunrise of the month in Philadelphia is 5:58 AM on August 1 and the latest sunrise is 28 minutes later at 6:27 AM on August 31.
The latest sunset is 8:14 PM on August 1 and the earliest sunset is 40 minutes earlier at 7:33 PM on August 31.
Daylight saving time is observed in Philadelphia during 2023, but it neither starts nor ends during August, so the entire month is in daylight saving time.
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.
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.
The figure below presents a compact representation of key lunar data for August 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.
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 August, falling from 58% to 37% over the course of the month.
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.
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 essentially constant during August, remaining within 0.2 miles per hour of 5.7 miles per hour throughout.
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.
The lowest daily average wind speed during August is 5.5 miles per hour on August 14.
The hourly average wind direction in Philadelphia throughout August is predominantly from the south, with a peak proportion of 36% on August 2.
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 essentially constant during August, remaining within 1°F of 74°F throughout.
The highest average surface water temperature during August is 74°F on August 10.
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.
The month of August in Philadelphia is reliably fully 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 August, increasing by 752°F, from 2,236°F to 2,988°F, over the course of the month.
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 gradually decreasing during August, falling by 0.7 kWh, from 6.3 kWh to 5.7 kWh, over the course of the month.
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.
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.
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.
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