ERA5 almanac comparison — 8 years of real data
Phoenix vs Tulum: weather in September
Phoenix is the clear winner for sun in September: 82% of days historically clear versus just 4% in Tulum — a 78-point gap across 8 years of ERA5 data. Tulum also sees measurably more rain than Phoenix this month (72% vs 10% of days). This isn't close.
Phoenix
AZ
- Clear days, September
- 82%
- Sample size
- n=240 days
- Avg high
- 101°F
- Early September (1st–15th)
- 82%
- Late September (16th–end)
- 81%
- Rain frequency
- 10% of days
Tulum
Mexico
- Clear days, September
- 4%
- Sample size
- n=240 days
- Avg high
- 88°F
- Early September (1st–15th)
- 5%
- Late September (16th–end)
- 3%
- Rain frequency
- 72% of days
Frequently asked
Is Phoenix or Tulum warmer in September?
Phoenix runs warmer by day in September. Phoenix averages highs of 101°F (highs n=240 days); Tulum averages highs of 88°F (highs n=240 days) (ERA5 2018–2025). Historical averages, not a forecast.
Does it rain more in Phoenix or Tulum in September?
Tulum is measurably wetter than Phoenix. Days with measurable rain: Phoenix 10%, Tulum 72% (n=240 and n=240 days). ERA5 2018–2025; historical, not a forecast.
Which is sunnier in September, Phoenix or Tulum?
Phoenix is the clear winner for sun in September: 82% of days historically clear versus just 4% in Tulum — a 78-point gap across 8 years of ERA5 data. Tulum also sees measurably more rain than Phoenix this month (72% vs 10% of days). This isn't close.
Compare Phoenix vs Tulum 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.