Hanoi, the capital of Vietnam, sits in the north of the country on the Red River delta, on a low, flat plain not far inland from the Gulf of Tonkin, at approximately 21.03°N, 105.85°E. Lying on the edge of the tropics, it has a humid subtropical climate (Köppen Cwa) with four distinct seasons — a genuine cool season sets it apart from the perpetually hot south — shaped by the East Asian monsoon, with cool, dry, sometimes chilly winters and hot, wet summers.

Summer, from May to September, is hot, humid and wet, with June and July the hottest months — average highs around 32–33°C and sultry nights — and high humidity that makes the heat feel oppressive. This is the rainy season, when the southwest monsoon brings heavy, frequent downpours and thunderstorms, often in the afternoon and evening, and late summer into autumn can bring typhoons off the Gulf of Tonkin, with strong winds and flooding rain.

Winter, from November to March, is cool and comparatively dry, with January the coolest month — average highs around 20°C and lows near 14–15°C, occasionally dropping close to 10°C during cold spells when northeast monsoon air pushes down from China. The season is often grey and overcast, and from February into March a persistent fine drizzle known as the cráchin dampens the city. This genuine cool season is unlike anything in tropical southern Vietnam.

Hanoi is wet, receiving around 1,680–1,760 mm of rain a year, overwhelmingly concentrated in the summer rainy season from May to September, when monthly totals are heavy; the winter is much drier, though the late-winter cráchin drizzle keeps the air damp. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Hanoi's defining feature is its true four-season subtropical climate — rare in Southeast Asia — with a genuinely cool, sometimes chilly winter driven by cold air spilling down from China on the northeast monsoon. The damp, misty cráchin drizzle of February and March is a distinctive local phenomenon, while autumn, dry and mild after the summer rains, is widely regarded as the most beautiful season in the city.

To follow any single measurement in Hanoi 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.