ERA5 almanac comparison — 8 years of real data
Aspen vs Houston: weather in September
Aspen edges out Houston for sun in September: 39% clear historically versus 30% (8-year ERA5 average, a 9-point gap). Houston also sees measurably more rain than Aspen this month (50% vs 23% of days). Both are viable — Aspen 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.
Aspen
CO
- Clear days, September
- 39%
- Sample size
- n=240 days
- Avg high
- 72°F
- Early September (1st–15th)
- 52%
- Late September (16th–end)
- 26%
- Rain frequency
- 23% of days
Houston
TX
- Clear days, September
- 30%
- Sample size
- n=240 days
- Avg high
- 88°F
- Early September (1st–15th)
- 28%
- Late September (16th–end)
- 32%
- Rain frequency
- 50% of days
Compare Aspen vs Houston 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.