ERA5 almanac comparison — 8 years of real data
Key West vs Tucson: weather in September
Tucson is the clear winner for sun in September: 70% of days historically clear versus just 11% in Key West — a 59-point gap across 8 years of ERA5 data. Key West also sees measurably more rain than Tucson this month (64% vs 20% of days). This isn't close.
Key West
FL
- Clear days, September
- 11%
- Sample size
- n=240 days
- Avg high
- 85°F
- Early September (1st–15th)
- 14%
- Late September (16th–end)
- 8%
- Rain frequency
- 64% of days
Tucson
AZ
- Clear days, September
- 70%
- Sample size
- n=240 days
- Avg high
- 96°F
- Early September (1st–15th)
- 72%
- Late September (16th–end)
- 69%
- Rain frequency
- 20% of days
Frequently asked
Is Key West or Tucson warmer in September?
Tucson runs warmer by day in September. Key West averages highs of 85°F (highs n=240 days); Tucson averages highs of 96°F (highs n=240 days) (ERA5 2018–2025). Historical averages, not a forecast.
Does it rain more in Key West or Tucson in September?
Key West is measurably wetter than Tucson. Days with measurable rain: Key West 64%, Tucson 20% (n=240 and n=240 days). ERA5 2018–2025; historical, not a forecast.
Which is sunnier in September, Key West or Tucson?
Tucson is the clear winner for sun in September: 70% of days historically clear versus just 11% in Key West — a 59-point gap across 8 years of ERA5 data. Key West also sees measurably more rain than Tucson this month (64% vs 20% of days). This isn't close.
Compare Key West vs Tucson 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.