Pittsburgh sits at the confluence of the Allegheny and Monongahela rivers in southwestern Pennsylvania, in a hilly landscape at the foot of the Appalachians at approximately 40.44°N, 79.99°W. It has a humid continental climate (Köppen Dfa/Cfa) — with warm, humid summers and cold winters — and it is among the cloudiest cities in the United States.

Summer, from June to August, is warm and humid, with July the warmest month — average highs around 28–29°C — and heatwaves that can exceed 33°C. It is the wettest season, with frequent afternoon thunderstorms, and the surrounding hills and rivers keep the humidity high, giving muggy, hazy days.

Winter, from December to February, is cold and persistently grey, with January the coldest month — average highs around 2°C and lows near -6°C. Snow falls regularly, around 110 cm a year, though it often thaws between storms, and the season is dominated by low cloud spilling over the Appalachians from the Great Lakes.

Pittsburgh receives around 960–1,000 mm of precipitation a year, spread fairly evenly through every month with a summer maximum from thunderstorms; its three-river confluence makes flooding a recurring hazard when heavy rain or snowmelt swells the valleys. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Pittsburgh ranks among the cloudiest major American cities, receiving only about 160 sunny days a year, as moisture from the Great Lakes spills over the Appalachian plateau and settles in the river valleys. Its three-river confluence, hemmed in by steep hills, has repeatedly flooded the low-lying downtown.

To follow any single measurement in Pittsburgh more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.