Bulgaria weather by month

In Sofia, 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 June 1 and lasts for 4.0 months, ending around October 1. The clearest month is August, when the sky is clear, mostly clear, or partly cloudy 80% of the time on average.

The cloudier part of the year begins around October 2 and lasts for 8.0 months, ending around May 31. The cloudiest month is February, when it is overcast or mostly cloudy 60% 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.

Wind in Sofia is steady company: average speeds sit near 7 km/h — calm — in every month of the year, with no meaningful windy or calm season.

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.

Sofia receives about 4.0 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 1.6 and 6.3 kWh/m².

The brighter stretch of the year lasts 6.1 months, from around Mar 19 to Sep 21. The brightest month is June, averaging about 6.2 kWh/m² (intense).

The dimmest month is December, down near 1.6 kWh/m² — roughly 74% less than the June peak.