Winter Weather in Philadelphia Pennsylvania, United States
Daily high temperatures are around 45°F, rarely falling below 27°F or exceeding 63°F. The lowest daily average high temperature is 40°F on January 24.
Daily low temperatures decrease by 5°F, from 36°F to 31°F, rarely falling below 13°F or exceeding 47°F. The lowest daily average low temperature is 26°F on January 31.
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 Winter in Philadelphia
The figure below shows you a compact characterization of the hourly average winter 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 Winter in Philadelphia
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 winter in Philadelphia experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 51% throughout the season. The highest chance of overcast or mostly cloudy conditions is 54% on January 7.
The clearest day of the winter is December 2, with clear, mostly clear, or partly cloudy conditions 51% 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 Winter in Philadelphia
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
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 winter is essentially constant, remaining around 24% 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 winter in Philadelphia, the chance of a day with only rain decreases from 24% to 18%, the chance of a day with mixed snow and rain increases from 2% to 5%, and the chance of a day with only snow increases from 1% to 3%.
Probability of Precipitation in the Winter in Philadelphia
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 winter in Philadelphia is decreasing, starting the season at 3.4 inches, when it rarely exceeds 5.7 inches or falls below 1.4 inches, and ending the season at 2.5 inches, when it rarely exceeds 4.5 inches or falls below 0.9 inches.
The lowest average 31-day accumulation is 2.1 inches on February 8.
Average Monthly Rainfall in the Winter in Philadelphia
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 winter in Philadelphia is increasing, starting the season at 1.7 inches, when it rarely exceeds 6.6 inches or falls below -0.0 inches, and ending the season at 4.3 inches, when it rarely exceeds 14.2 inches.
The highest average 31-day accumulation is 6.5 inches on January 26.
Average Monthly Snowfall in the Winter in Philadelphia
Over the course of the winter in Philadelphia, the length of the day is rapidly increasing. From the start to the end of the season, the length of the day increases by 1 hour, 44 minutes, implying an average daily increase of 1 minute, 10 seconds, and weekly increase of 8 minutes, 7 seconds.
The shortest day of the winter is December 22, with 9 hours, 20 minutes of daylight and the longest day is February 29, with 11 hours, 17 minutes of daylight.
Hours of Daylight and Twilight in the Winter in Philadelphia
The latest sunrise of the winter in Philadelphia is 7:22 AM on January 4 and the earliest sunrise is 48 minutes earlier at 6:34 AM on February 29.
The earliest sunset is 4:35 PM on December 7 and the latest sunset is 1 hour, 17 minutes later at 5:52 PM on February 29.
Daylight saving time is observed in Philadelphia during 2023, but it neither starts nor ends during the winter, so the entire season is in standard 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.
Sunrise & Sunset with Twilight and Daylight Saving Time in the Winter in Philadelphia
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 Winter in Philadelphia
The figure below presents a compact representation of key lunar data for the winter 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 Winter in Philadelphia
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 essentially constant during the winter, remaining around 0% throughout.
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 Winter in Philadelphia
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
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 winter, increasing from 7.8 miles per hour to 9.1 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.
The highest daily average wind speed during the winter is 9.2 miles per hour on February 27.
Average Wind Speed in the Winter in Philadelphia
The hourly average wind direction in Philadelphia throughout the winter is predominantly from the west, with a peak proportion of 45% on January 17.
Wind Direction in the Winter in Philadelphia
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 winter, falling by 11°F, from 51°F to 39°F, over the course of the season.
The lowest average surface water temperature during the winter is 39°F on February 20.
Average Water Temperature in the Winter in Philadelphia
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 winter in Philadelphia is very likely fully outside of the growing season, with the chance that a given day is in the growing season reaching a low of -0% on December 25.
Time Spent in Various Temperature Bands and the Growing Season in the Winter in Philadelphia
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
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 very rapidly decreasing during the winter, decreasing by 3,862°F, from 3,888°F to 26°F, over the course of the season.
Growing Degree Days in the Winter in Philadelphia
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 increasing during the winter, rising by 1.4 kWh, from 2.1 kWh to 3.5 kWh, over the course of the season.
The lowest average daily incident shortwave solar energy during the winter is 1.8 kWh on December 23.
Average Daily Incident Shortwave Solar Energy in the Winter in Philadelphia
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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