Monthly weather forecast and climate
Pennsylvania, USA

Flag of Pennsylvania, USA
Flag of Pennsylvania, USA

The climate of Pennsylvania

Pennsylvania experiences a humid continental climate with hot and humid summers and cold winters (Köppen climate classification Dfa) in the majority of the state. Delaware in the southeast, Maryland in the south, West Virginia in the southwest, Ohio in the west, New York in the north, the Canadian province of Ontario in the northwest, and New Jersey in the east, border the state. The southeast corner displays a humid subtropical climate (Köppen Cfa) due to the diverse topography of the state.

Pennsylvania, the Keystone State, is part of the Mid-Atlantic and Northeast states of America and consists of mountains, high plains, rivers, river valleys, coastal plains, lakes, and many other natural features. The Appalachian Mountains divide the state into two parts - the western part is colder than the east and is more rainy and snowy. Lake Erie, the largest water body with 51 miles of coastal shoreline, lies in the northwest of the state, while the Allegheny Plateau is in the east. Pennsylvania also has 57 miles of coastline along the Delaware Estuary but exceptionally, does not have a border with the Atlantic Ocean.

Pennsylvania has summer day temperatures in the 75°F (23.9°C) to 95°F (35°C) range, while nights are in 55°F (12.8°C) to 70°F (21.1°C) span. Winter highs are 33°F (0.6°C) to 45°F (7.2°C), while lows register in the 19°F (-7.2°C) to 30°F (-1.1°C) range. July is the peak of summer, which rarely touches 100°F (37.8°C), while January is the trough of winter when the temperatures often go below 0°F (-17.8°C). Spring is wet and prone to flooding, while autumn is temperate and colorful in the state. Fog is frequent during the winter, and clouds routinely don the skies. Pennsylvania is prone to tropical cyclones, tornadoes, and snowstorms - however, the record 24-hour rainfall is 13.5" (343mm), and snowfall is 38" (965mm).

The mountainous interior of Pennsylvania is cold during the winter; the west - particularly the northwest areas near Lake Erie receive abundant snowfall over 100" (2540mm) and heavy rainfall.
Pennsylvania has evenly distributed rainfall throughout the year that averages 42" (1067mm). July receives peak rainfall, while February is the snowiest month of the year. Snowfall registers 23" (584mm) statewide with the mountains and highlands recording far more than the average. Eastern valleys that lie on the leeward side of the mountains record less rain and warm temperatures. Pennsylvania receives ample rainfall with an average of 180 days of sunshine during the year - cloudy skies are common in the state throughout the year.

Phoenixville recorded Pennsylvania's highest temperature of 111°F (43.9°C) on July 9 and 10, 1936, while Smethport recorded the lowest temperature of -42°F (-41.1°C) on January 5, 1904.

The best time to visit Pennsylvania

Summers are warm to hot and humid in the state, but few days go beyond 95°F (35°C). Rainfall peaks during the summer with a chance of thunderstorms. Spring is warm, wet, and prone to floods, especially in March and April. Autumn is mild in the early days and gradually cools down with the progress of the season - the fall foliage is extravagantly beautiful.
The best time to visit Pennsylvania is from May to October, but it is a good idea to avoid the rush of the summer crowd, which is the peak tourist season due to school vacations.

The worst time to visit Pennsylvania

December to February is the worst time to visit Pennsylvania due to the extreme cold. The ground is white, the roads are icy, and the air is chilly. Snowstorms are frequent during the winter and deposit a large amount of snow. Blizzards can close roads and even stall highways and towns for long periods. Fog often accompanies the dark clouds, and sunshine is at a premium.
Most of the tourists leave Pennsylvania by November at the end of the fall season, and only budget travelers and snow enthusiasts remain during the winter.

Weather hazards

Pennsylvania is vulnerable to thunderstorms, especially in the mountains and highlands that occur in late spring and early summer. March and April are prone to flooding in many parts of the state. Tornadoes hit the state regularly until August and average approximately 30 during the year. Tropical cyclones are common during the summer but rarely create landfalls, and the wettest recorded until date brought almost 19" (483mm) of rain - hurricane-force winds are the hallmark of peak category cyclones the Philadelphia area. Snowstorms are frequent during the winter, and a few are of high intensity.

Weather in January

January is generally the coldest month of the year in Pennsylvania as the temperatures plummet below 0°F (-17.8°C) in many places. The average low temperatures are in the frigid 12°F (-11.1°C) to 20°F (-6.7°C) zone, and the average high temperatures are in the 30°F (-1.1°C) to 40°F (4.4°C) range. Weather in January »

Weather in February

February is a cold winter month in Pennsylvania as the days rarely go above 45°F (7.2°C), and the nights are well below freezing. Jamestown, New Castle, and Warren, all in the west, register night temperatures below 20°F (-6.7°C). Snowstorms and blizzards frequently occur during the winter as the plows continuously strive to keep the roads and highways free of snow. Weather in February »

Weather in March

March signals the arrival of the spring season in Pennsylvania. Warmer days register in the 40°F (4.4°C) to 50°F (10°C) range, while the nights are still cold in the 25°F (-3.9°C) to 35°F (1.7°C) range. Spring is rainy to the tune of 3" (76mm) to 4" (102mm) statewide. Weather in March »

Weather in April

April is a warm and wet spring month in Pennsylvania with temperate days and mild nights. Spring season is at its peak in the state to the delight of everybody. The average high temperatures are in the 55°F (12.8°C) to 65°F (18.3°C) range, while the average low temperatures are in the mild 35°F (1.7°C) to 45°F (7.2°C). Rainfall is moderate to the tune of 3" (76mm) to 4" (102mm) as cloud cover is common in the skies. Weather in April »

Weather in May

May has pleasant temperatures and starts the tourist season earnestly in Pennsylvania as spring spreads its wings fully. The average high temperatures are in the warm 65°F (18.3°C) to 75°F (23.9°C) range, while the average low temperatures are in the mild range of 40°F (4.4°C) to 50°F (10°C). Weather in May »

Weather in June

June is one of the best times to visit Pennsylvania, with abundant sunshine everywhere. The average high temperatures are in the delightful 75°F (23.9°C) to 84°F (28.9°C) range, while average low temperatures are warm 54°F (12.2°C) to 60°F (15.6°C). Sunshine is adequate on the western side and plenty on the eastern side along with a high degree of humidity. Weather in June »

Weather in July

July is usually the hottest month of the year in Pennsylvania, with the average high temperatures in the state of 79°F (26.1°C) to 87°F (30.6°C) and the average night temperatures of 54°F (12.2°C) to 63°F (17.2°C). Pittsburgh in the west averages between 63°F (17.2°C) to 83°F (28.3°C), while Philadelphia in the southeast corner is between 69°F (20.6°C) and 87°F (30.6°C). More than 20 days see the presence of sun with the rest being cloudy and rainy. Weather in July »

Weather in August

August is a hot and humid summer month in Pennsylvania with a combination of sunny and cloudy days. Sunshine spans for nearly 20 days during the month, and midday temperatures are the hottest. The average high temperatures are in the hot range of 77°F (25°C) to 87°F (30.6°C), while the average low temperatures are 53°F (11.7°C) to 68°F (20°C). Weather in August »

Weather in September

September marks the start of the autumn season that covers the landscape with beautiful colors. The leaves start to turn, and by the end of September, the lush green landscape adorns a colorful cloak ranging from orange, yellow, amber, gold to red, and magenta. The average high temperatures are in the comfortable 72°F (22.2°C) to 80°F (26.7°C) range, while the night temperatures drop to 46°F (7.8°C) to 60°F (15.6°C). Weather in September »

Weather in October

October is an excellent time to experience the richness of the fall foliage in Pennsylvania. The days are pleasant and average highs are in the 58°F (14.4°C) to 67°F (19.4°C) range, while nights are cold as average lows drop to 40°F (4.4°C). Fall foliage is at its peak in the state by mid-October as fantastic scenery unfolds in the backdrop of the mountains. Weather in October »

Weather in November

November ends the autumn season in Pennsylvania with cold nights that range from 30°F (-1.1°C) to 40°F (4.4°C). The average high temperatures are in the mild 45°F (7.2°C) to 55°F (12.8°C) range, and the sunlight gradually decreases by the end of the month. Western Pennsylvania has roughly 10 days of sun during the month, while the eastern part is comparatively warmer at 15 days. Weather in November »

Weather in December

December begins the winter in Pennsylvania with the average high temperatures in the 34°F (1.1°C) to 45°F (7.2°C) range and the average low temperatures in the cold 18°F (-7.8°C) to 30°F (-1.1°C) range. The western half of the state is prone to cold weather with average low temperatures of 18°F (-7.8°C) in Bradford and 22°F (-5.6°C) in Indiana, while the eastern half is relatively warm with average low temperatures of 27°F (-2.8°C) in Norristown and 30°F (-1.1°C) in Philadelphia. Snowfall is heavy in the highlands and mountains, while rainfall is to the tune of 3" (76mm) to 4" (102mm). Weather in December »
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