Average Weather in Pittsburgh Pennsylvania, United States
In Pittsburgh, the temperature typically varies from 23°F to 83°F over the course of the year, and is rarely below 7°F or above 91°F.
The warm season lasts for 3.8 months, from May 24 to September 19, with an average daily high temperature above 74°F. The hottest day of the year is July 20, with an average high of 83°F and low of 66°F.
The cold season lasts for 3.1 months, from December 1 to March 4, with an average daily high temperature below 47°F. The coldest day of the year is January 29, with an average low of 23°F and high of 37°F.
Average High and Low Temperature
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
The length of the day in Pittsburgh varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 17 minutes of daylight; the longest day is June 21, with 15 hours, 4 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:49 AM on June 14, and the latest sunrise is 2 hours, 5 minutes later at 7:53 AM on November 4. The earliest sunset is at 4:53 PM on December 7, and the latest sunset is 4 hours, 1 minute later at 8:54 PM on June 27.
Daylight saving time (DST) is observed in Pittsburgh during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
In Pittsburgh, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Pittsburgh begins around May 14 and lasts for 5.9 months, ending around November 12. On August 27, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 65% of the time, and overcast or mostly cloudy 35% of the time.
The cloudier part of the year begins around November 12 and lasts for 6.1 months, ending around May 14. On January 12, the cloudiest day of the year, the sky is overcast or mostly cloudy 69% of the time, and clear, mostly clear, or partly cloudy 31% of the time.
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Pittsburgh varies throughout the year.
The wetter season lasts 5.0 months, from March 21 to August 20, with a greater than 31% chance of a given day being a wet day. The chance of a wet day peaks at 41% on June 16.
The drier season lasts 7.0 months, from August 20 to March 21. The smallest chance of a wet day is 20% on January 30.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 41% on June 16.
Daily Chance of Precipitation
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 in the year. Pittsburgh experiences some seasonal variation in monthly rainfall.
Rain falls throughout the year in Pittsburgh. The most rain falls during the 31 days centered around June 13, with an average total accumulation of 3.4 inches.
The least rain falls around February 6, with and average total accumulation of 1.5 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day in the year. Pittsburgh experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 3.9 months, from November 30 to March 27, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around February 12, with an average total liquid-equivalent accumulation of 0.3 inches.
The snowless period of the year lasts for 8.1 months, from March 27 to November 30. The least snow falls around July 26, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
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.
Pittsburgh experiences significant seasonal variation in the perceived humidity.
The muggier period of the year lasts for 3.6 months, from May 31 to September 19, during which time the comfort level is muggy, oppressive, or miserable at least 10% of the time. The muggiest day of the year is July 29, with muggy conditions 40% of the time.
The least muggy day of the year is December 4, when muggy conditions are essentially unheard of.
Humidity Comfort Levels
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 Pittsburgh experiences mildly seasonal variation over the course of the year.
The windier part of the year lasts for 5.5 months, from November 14 to April 28, with average wind speeds of more than 2.7 miles per hour. The windiest day of the year is February 2, with an average hourly wind speed of 3.5 miles per hour.
The calmer time of year lasts for 6.5 months, from April 28 to November 14. The calmest day of the year is August 4, with an average hourly wind speed of 1.8 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Pittsburgh varies throughout the year.
The wind is most often from the south for 1.1 months, from September 2 to October 4, with a peak percentage of 35% on November 15. The wind is most often from the west for 11 months, from October 4 to September 2, with a peak percentage of 51% on January 30.
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 very significant seasonal variation over the course of the year.
The brighter period of the year lasts for 3.8 months, from May 2 to August 28, with an average daily incident shortwave energy per square meter above 5.7 kWh. The brightest day of the year is July 2, with an average of 6.8 kWh.
The darker period of the year lasts for 3.4 months, from November 5 to February 15, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest day of the year is December 25, with an average of 1.6 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Pittsburgh are 40.441 deg latitude, -79.996 deg longitude, and 938 ft elevation.
The topography within 2 miles of Pittsburgh contains significant variations in elevation, with a maximum elevation change of 535 feet, and an average elevation above sea level of 887 feet. Within 10 miles also contains significant variations in elevation (663 feet). Within 50 miles contains large variations in elevation (2,365 feet).
The area within 2 miles of Pittsburgh is covered by artificial surfaces (97%), within 10 miles by artificial surfaces (79%) and trees (18%), and within 50 miles by trees (63%) and cropland (23%).
This report illustrates the typical weather in Pittsburgh, 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 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Pittsburgh.
For each station, the records are corrected for the elevation difference between that station and Pittsburgh 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 Pittsburgh is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Pittsburgh and a given station.
The stations contributing to this reconstruction are: Allegheny County Airport (54%, 11 kilometers, southeast), Pittsburgh International Airport (33%, 19 kilometers, west), and Butler-Graham Airport (13%, 38 kilometers, north).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports and weather stations are provided by AskGeo.com .