Colombo, the largest city and commercial capital of Sri Lanka, sits on the island's west coast on the Indian Ocean, just 7 degrees north of the equator at approximately 6.93°N, 79.85°E. It has a tropical monsoon climate (Köppen Am) — hot, humid and rainy year-round with almost no change in temperature — where the year is defined not by hot and cold but by the rhythm of two monsoons and the inter-monsoon rains.

There is no summer in the temperate sense: temperatures barely change, with daytime highs around 30–32°C every month and warm, humid nights near 25°C. Humidity stays high all year, often above 70–80%, so the heat feels sticky, tempered only by sea breezes off the Indian Ocean. March and April, between the monsoons, are typically the hottest and most humid months before the main rains arrive.

Nor is there a true winter, but the driest, sunniest and most comfortable weather comes from around December to March, during the northeast monsoon, which brings relatively little rain to Colombo on the island's western side. Temperatures remain warm and steady, and this drier stretch, with its clearer skies, is comfortably the best time to visit the city.

Colombo is very wet, receiving on the order of 2,400 mm of rain a year, delivered mainly by the southwest monsoon (roughly May to September, peaking around May and June) and boosted by the inter-monsoon rains of October and November, when thunderstorms are frequent. Even the 'drier' months see some rain, often as heavy afternoon downpours. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Colombo's weather is governed by the two monsoons that sweep the Indian Ocean: the southwest monsoon, which brings the heaviest rain to the city and the island's southwestern quarter, and the northeast monsoon, which waters the far side of the island while leaving Colombo drier. The inter-monsoon periods bring dramatic thunderstorms, and the island's equatorial position keeps it warm, green and humid throughout the year, largely outside the main path of tropical cyclones.

To follow any single measurement in Colombo 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.