Washington, D.C., the capital of the United States, sits on the Potomac River in the Mid-Atlantic region, at the boundary between the humid subtropical and humid continental zones at approximately 38.90°N, 77.04°W. It has a humid subtropical climate (Köppen Cfa) with hot, humid summers and cool to cold winters, and four distinct seasons, its inland-tending position giving it more heat and humidity than the coast further north.

Summer, from June to August, is hot and notably humid, with July the warmest month — average highs around 31–32°C — and muggy spells, built on the region's low, swampy origins, that regularly push the heat index past 38°C. Afternoon and evening thunderstorms are frequent, sometimes severe, and the sultry heat lingers into the night. It is the wettest season, dominated by convective storms.

Winter, from December to February, is cool to cold, with January the coldest month — average highs around 6–47°C and lows near -2°C. It is changeable: mild spells alternate with cold outbreaks from Canada, and precipitation can fall as rain, sleet, freezing rain or snow. Snowfall is moderate and highly variable — some winters are nearly snowless, while occasional nor'easters or 'Snowmageddon'-type storms can bring heavy accumulations.

Washington receives around 1,000–1,050 mm of precipitation a year, spread fairly evenly through every month with a summer thunderstorm peak; there is no dry season. Occasional tropical systems can bring heavy rain in late summer and autumn. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Washington's summers are famous for their oppressive humidity — a legacy of the low-lying, once-marshy terrain along the Potomac — which makes the heat feel heavier than the temperature alone. Its winters sit on a knife-edge between rain and snow, so a single storm's track can mean anything from a cold rain to a paralysing blizzard, while autumn brings crisp air and vivid foliage across the region.

To follow any single measurement in Washington DC 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.