ERA5 almanac comparison — 8 years of real data
London vs Madrid: weather in September
Madrid is the clear winner for sun in September: 62% of days historically clear versus just 14% in London — a 48-point gap across 8 years of ERA5 data. This isn't close.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific September. For this
week’s actual forecast, each destination links to its live page below.
London
GB
- Clear days, September
- 14%
- Sample size
- n=240 days
- Avg high
- 68°F
- Early September (1st–15th)
- 20%
- Late September (16th–end)
- 9%
Madrid
ES
- Clear days, September
- 62%
- Sample size
- n=240 days
- Avg high
- 80°F
- Early September (1st–15th)
- 68%
- Late September (16th–end)
- 56%
Compare London vs Madrid in another month
All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.