ERA5 almanac comparison — 8 years of real data
Birmingham vs Charleston: weather in September
Birmingham edges out Charleston for sun in September: 49% clear historically versus 32% (8-year ERA5 average, a 17-point gap). Charleston also sees measurably more rain than Birmingham this month (46% vs 31% of days). Both are viable — Birmingham is the safer bet.
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.
Birmingham
AL
- Clear days, September
- 49%
- Sample size
- n=240 days
- Avg high
- 86°F
- Early September (1st–15th)
- 44%
- Late September (16th–end)
- 54%
- Rain frequency
- 31% of days
Charleston
SC
- Clear days, September
- 32%
- Sample size
- n=240 days
- Avg high
- 83°F
- Early September (1st–15th)
- 28%
- Late September (16th–end)
- 37%
- Rain frequency
- 46% of days
Compare Birmingham vs Charleston 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.