Tonga weather by month

In Nuku‘alofa, the average share of the sky covered by clouds shows mild seasonal variation over the course of the year.

The clearer part of the year begins around July 7 and lasts for 3.3 months, ending around October 14. The clearest month is September, when the sky is clear, mostly clear, or partly cloudy 51% of the time on average.

The cloudier part of the year begins around February 23 and lasts for 1.0 months, ending around March 25. The cloudiest month is June, when it is overcast or mostly cloudy 57% 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 Nuku‘alofa is typically breezy, near 24 km/h, and varies little with the seasons.

The windier part of the year lasts 4.1 months, from around Apr 7 to Aug 8. The windiest month is April, averaging about 25 km/h (breezy).

The calmer part of the year runs from around Jan 14 to Apr 6, with February the calmest month at about 23 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.

Nuku‘alofa receives about 5.1 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 3.3 and 6.9 kWh/m².

The brighter stretch of the year lasts 6.3 months, from around Sep 19 to Mar 29. The brightest month is December, averaging about 6.8 kWh/m² (intense).

The dimmest month is June, down near 3.3 kWh/m² — roughly 51% less than the December peak.