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" (342.9mm), and snowfall is 38" (965.2mm).
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" (1066.8mm). July receives peak rainfall, while February is the snowiest month of the year. Snowfall registers 23" (584.2mm) 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.
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" (482.6mm) 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. Allentown in the east averages between 20°F (-6.7°C) to 36°F (2.2°C), while Bradford in the west is between 12°F (-11.1°C) to 30°F (-1.1°C). Snowfall is heavy and averages 15" (381mm) - Erie alone accounts for 30" (762mm) of snow in January. The daylight is short, and the sunshine lasts hardly for 4 to 5 hours a day as cloud cover spreads over the entire state. January attracts snow enthusiasts for activities like sleigh riding, dog sledding, snowshoeing, wind skating, and ice fishing, among others. Expect deep snowpack in the mountains and keep an eye for snowstorms and severe weather. Some of the Pennsylvania roads are the most dangerous to drive in the United States during winter -, while it is a good idea to avoid the state a visit during January at least stay away from driving in the rough weather!
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. Snowfall is in the average 10" (254mm) to 12" (304.8mm) range in the lowlands, while the highlands receive at least twice that. The February sun is just 35% to 40% of the peak in the majority of the state, while the southeast corner averages 50%. Cloudy skies are typical, while rain is mostly in the form of ice and snow. As winter knocks in the state, the picturesquely white landscape in the cloak of snow appears to be the setting of storybook scenery, particularly in the state parks in the backdrop of mountains! Overall, February is not a good time to visit Pennsylvania due to the intense cold weather.
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" (76.2mm) to 4" (101.6mm) statewide. Snowfall is in fair amounts in most places with the average 5" (127mm) to 7" (177.8mm). Erie in the west records 14" (355.6mm) of snow, while State College in the east registers 10.3" (261.6mm). An average of 14 days have sunshine in March, and the daylight extends to 11 hours. Pennsylvania is prone to floods in some places due to the melting of snow and the presence of rain. Spring brings freshness in the air and sweetness in the water as the flora and fauna dance with joy. Early bird discounts wait during the spring season, as the tourist season is yet to pick up in full swing. March is chilly at times, and it is better to dress in layers to protect from the wind and rain.
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" (76.2mm) to 4" (101.6mm) as cloud cover is common in the skies. Snowfall usually subsides by April with the last remnants of snow present on the ground. Sunlight improves to approximately 60% of the peak with long, warm days that bring an atmosphere of gaiety. Abundant freshwater in the creeks, streams, lakes, and rivers is cold for swimming but perfect for anglers who throw their hooks with renewed vigor to trap varieties of fish. April in Pennsylvania sees a rise in tourist numbers due to the temperate weather and the off-season discounts for early birds.
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). Harrisburg, the capital of Pennsylvania in the east, has average temperatures in the comfortable 51°F (10.6°C) to 72°F (22.2°C) range, while Jamestown in the west is between a mild 45°F (7.2°C) to warm 68°F (20°C). Most of the snow melts in the highlands, and upper mountain ranges by May and rainfall of 4" (101.6mm) to 5" (127mm) adds freshwater to the water bodies that come roaring down the hills. Sunshine makes a glorious comeback by May as spring becomes noisy amid the cacophony of birds and animals. Watch out for black bears and other animals that desperately hunt for food after facing a shortage during the winter, especially, while exploring the state parks or the mountain trails - a bear spray is a proven accessory to carry on hikes!
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. Long days stretch up to 12 hours and provide plenty of sunlight for enjoying outdoor activities. Pennsylvania skies are rarely blue and clear, and it is routine to expect at least a few clouds. June is usually wet as rainfall accumulates to 4" (101.6mm) to 5" (127mm) with frequent heavy showers. Summer is a great time to have a few light drinks and enjoy the various festivals or ride the white rapids in rivers such as the Youghiogheny at Ohiopyle State Park. Beware; though summer is the peak tourist season, there is always a more than even chance of a tropical cyclone or tornado, crashing vacation plans!
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 in July see the presence of sun with the rest being cloudy and rainy. Plenty of sunshine ushers in long days exceeding 13 hours of daylight suitable for outdoor activities. July is the wettest month with an average of 5" (127mm) of rain - the western side of the state is rainier than the eastern one. The lakeside towns provide warm waters suitable for swimming and water activities. Summer is the perfect time for camping, fishing, visiting zoos and national parks, or just dropping into one of the many caves in the state. While rain is imminent, light summer clothing is apt for wearing in the season.
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). Norristown in the southeastern corner of the state averages between 64°F (17.8°C) to 87°F (30.6°C), Lancaster in the south is between 63°F (17.2°C) to 84°F (28.9°C), while Altoona in the west ranges between 58°F (14.4°C) to 80°F (26.7°C). August has plenty of rainfall and prone to thunderstorms or odd cyclones. Summer days provide a barrage of activities to the swelling crowds - it is the perfect time to enjoy the coolness of the water in the scorching sun. Light sweatshirts are suitable to wear in the sun - note that the ultraviolet index of the sun is in the highest range in August, so take adequate protection, while venturing out in the heat.
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). Sunshine is ample in September, with an average of 19 sunny days. Fall is prone to cold breezes, especially in the evenings - so, it is a good idea to dress in layers. An odd storm may pass through early fall with the likelihood of heavy rain. Fall also spots active wildlife who scramble across the land in search of food. The vibrant colors during the autumn make for some great experiences, and the period around the fourth week of September is one of the best times of the year in Pennsylvania to carry a camera!
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. It is an excellent time to visit Pennsylvania with pleasant weather in the lap of beautiful nature and spotting wildlife. Uniontown in the west averages between 40°F (4.4°C) to 65°F (18.3°C), Bradford is a little cold between 35°F (1.7°C) to 58°F (14.4°C), while Chambersburg in the east is between 43°F (6.1°C) to 64°F (17.8°C). October mornings are hazy at times; middays are usually warm and sunny, while evenings tend to be breezy and a little cold - jackets are generally a better alternative to bear the cold and rain. Rain is moderate in late autumn, and the sun regularly marks its presence in the skies.
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. The foliage fades by mid-November, and crispy leaves fill the trails as the trees start to look barer in the absence of leaves. Rain is frequent but takes the form of drizzles as the wind gathers speed. November witnesses the first snowfall in many places - the western part of the state receives the first snowflakes and generally registers more snow than the east. Driving on the scenic roadways, trailing and biking in the mountains, and boating in the rivers and lakes are some of the best ways to enjoy the fall season. November is also the last of the fishing and hunting months before winter sets in.
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" (76.2mm) to 4" (101.6mm). Regions around Lake Erie are the cloudiest in the state with only 5 days of sunshine, while the rest of the state averages around 10. Chilly winds blow during the winter that makes the air seem colder than it is on the thermometer reading. The Philadelphia landscape is mostly white in December, and the severe cold necessitates warm winter clothes, gloves, boots, and caps during Christmas celebrations!.