ERA5 almanac comparison — 8 years of real data
Martha's Vineyard vs San Antonio: weather in September
San Antonio edges out Martha's Vineyard for sun in September: 36% clear historically versus 27% (8-year ERA5 average, a 9-point gap). Both are viable — San Antonio is the safer bet.
Martha's Vineyard
MA
- Clear days, September
- 27%
- Sample size
- n=240 days
- Avg high
- 72°F
- Early September (1st–15th)
- 39%
- Late September (16th–end)
- 15%
- Rain frequency
- 34% of days
San Antonio
TX
- Clear days, September
- 36%
- Sample size
- n=240 days
- Avg high
- 92°F
- Early September (1st–15th)
- 30%
- Late September (16th–end)
- 42%
- Rain frequency
- 31% of days
Frequently asked
Is Martha's Vineyard or San Antonio warmer in September?
San Antonio runs warmer by day in September. Martha's Vineyard averages highs of 72°F (highs n=240 days); San Antonio averages highs of 92°F (highs n=240 days) (ERA5 2018–2025). Historical averages, not a forecast.
Does it rain more in Martha's Vineyard or San Antonio in September?
Days with measurable rain: Martha's Vineyard 34%, San Antonio 31% (n=240 and n=240 days). ERA5 2018–2025; historical, not a forecast.
Which is sunnier in September, Martha's Vineyard or San Antonio?
San Antonio edges out Martha's Vineyard for sun in September: 36% clear historically versus 27% (8-year ERA5 average, a 9-point gap). Both are viable — San Antonio is the safer bet.
Compare Martha's Vineyard vs San Antonio 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 forecast for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.