Pennsylvania Annual Temperatures and Extremes

Pennsylvania's Temperature Records

Hottest temperature ever recorded: 111 F, Phoenixville, southeastern Pennsylvania, 7/10/1936 Coldest temperature ever recorded: -42 F, Smethport, northern Pennsylvania, 1/5/1904 Hottest location ranked by highest average annual temperature: Marcus Hook, southeastern Pennsylvania, 56.1 F Coldest location ranked by lowest average annual temperature: Pleasant Mount, northeastern Pennsylvania, 43.4 F During the summer of 2010, Philadelphia set a new record for number of days with the temperature equal or greater than 90 degrees with 55 days. From June 29 - July 11, daily record highs in Philadelphia are 100 F or higher. During the summer months of June - August, 40 days possess all-time record highs of 100 F or higher.

Across Pennsylvania, temperatures generally remain between zero and 100° F and average from near 47 in the north-central mountains to 57° F annually in the extreme southeast. The highest temperature of record, 111° F, was observed in Phoenixville on July 9 and 10, 1936, while the record low of -42° F occurred at Smethport on January 5, 1904.

Summers are generally warm, averaging about 70 along Lake Erie to 75° F in southeastern counties. High temperatures, 90° F or above, occur on an average of 10 to 20 days per year in most sections; but occasionally southeastern localities may experience a season with as many as 30 such days, while the extreme northwest averages as few as four such days. There are places such as adjacent to Lake Erie and at higher elevations where readings of 100° F have never been reached. Daily temperatures during the warm season usually have a range of about 20° F over much of the State, while the daily range in winter is several degrees less. During the coldest months, temperatures average near freezing with daily minimum sometimes 0° F or lower. Freezing temperatures occur on the average 100 or more days annually with the greatest number of occurrences in the mountainous regions. At a few sites, freezing temperatures have occurred during all months of the year and below 0° F readings from November to April, inclusive. Freezing temperatures occur on the average 100 or more days annually with the greatest number of occurrences in the mountainous regions. At a few sites, freezing temperatures have occurred during all months of the year and below 0° F readings from November to April, inclusive.

Differences in temperatures over the various parts of Pennsylvania no less pronounced in summer than in winter. The warmest days are found in the interior rather than near the coast in summer. The average daily maximum temperature at mid-summer exceeds 92 at Goldsboro and Fayetteville, for example, while on the southernmost part of the coast it is 89° F. The mid-July average afternoon high temperature atop Mount Mitchell is only 68, while over widely populated areas in the Mountain Division the figure is around 85° F. Morning temperatures average about 20° F degrees lower than those in the afternoon except along the immediate coast, where the daily range is only 10 to 15 degrees.

Autumn is the season of most rapidly changing temperature, the daily downward trend being greater than the corresponding rise in spring. The drop-off is greatest during October, and continues at a rapid pace in November, so that average daily temperatures by the end of that month are within about five degrees of the lowest point of the year.

Pennsylvania precipitation averages and extremes, Philadelphia climate records and averages, Top 10 climate extremes, precipitation data for all U.S. states
Data source: National Climatic Data Center