Sri Lanka weather by month

In Colombo, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.

The clearer part of the year begins around December 8 and lasts for 4.7 months, ending around April 29. The clearest month is March, when the sky is clear, mostly clear, or partly cloudy 61% of the time on average.

The cloudier part of the year begins around April 30 and lasts for 7.3 months, ending around December 7. The cloudiest month is July, when it is overcast or mostly cloudy 86% of the time.

This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.

Across the year, average wind speed in Colombo is typically light breeze, near 15 km/h, and varies a lot with the seasons.

The windier part of the year lasts 4.8 months, from around May 10 to Oct 3. The windiest month is June, averaging about 20 km/h (light breeze).

The calmer part of the year runs from around Jan 31 to May 9, with March the calmest month at about 9 km/h.

Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.

Colombo receives about 5.3 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 4.6 and 6.3 kWh/m².

The brighter stretch of the year lasts 3.9 months, from around Jan 6 to May 3. The brightest month is March, averaging about 6.3 kWh/m² (intense).

The dimmest month is November, down near 4.7 kWh/m² — roughly 26% less than the March peak.