Sao Tome and Principe weather by month

In São Tomé, the average share of the sky covered by clouds shows moderate seasonal variation over the course of the year.

The clearer part of the year begins around May 29 and lasts for 4.4 months, ending around October 9. The clearest month is June, when the sky is clear, mostly clear, or partly cloudy 41% of the time on average.

The cloudier part of the year begins around December 24 and lasts for 5.1 months, ending around May 28. The cloudiest month is March, when it is overcast or mostly cloudy 79% 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 São Tomé is typically light breeze, near 16 km/h, and varies moderately with the seasons.

The windier part of the year lasts 5.0 months, from around May 20 to Oct 19. The windiest month is July, averaging about 20 km/h (breezy).

The calmer part of the year runs from around Oct 20 to May 19, with January the calmest month at about 12 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.

São Tomé receives about 5.2 kWh/m² a day of solar energy — bright — and it stays remarkably steady, holding between 4.9 and 5.5 kWh/m² all year. For solar panels, output here is a flat line, not a seasonal wave.