ERA5 almanac comparison — 8 years of real data
Cancún vs San Antonio: weather in September
San Antonio is the clear winner for sun in September: 36% of days historically clear versus just 5% in Cancún — a 31-point gap across 8 years of ERA5 data. Cancún also sees measurably more rain than San Antonio this month (71% vs 31% of days). This isn't close.
Cancún
Mexico
- Clear days, September
- 5%
- Sample size
- n=240 days
- Avg high
- 88°F
- Early September (1st–15th)
- 5%
- Late September (16th–end)
- 5%
- Rain frequency
- 71% 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 Cancún or San Antonio warmer in September?
San Antonio runs warmer by day in September. Cancún averages highs of 88°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 Cancún or San Antonio in September?
Cancún is measurably wetter than San Antonio. Days with measurable rain: Cancún 71%, San Antonio 31% (n=240 and n=240 days). ERA5 2018–2025; historical, not a forecast.
Which is sunnier in September, Cancún or San Antonio?
San Antonio is the clear winner for sun in September: 36% of days historically clear versus just 5% in Cancún — a 31-point gap across 8 years of ERA5 data. Cancún also sees measurably more rain than San Antonio this month (71% vs 31% of days). This isn't close.
Compare Cancún 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.