ERA5 almanac comparison — 8 years of real data
Boston vs Park City: weather in September
Essentially a tie in September: Boston is 31% clear historically, Park City is 30% clear (8-year ERA5 average) — within the noise. Avg high 74°F vs 70°F. Pick based on flight time or price, not weather — the weather won't decide this one for you.
Boston
MA
- Clear days, September
- 31%
- Sample size
- n=240 days
- Avg high
- 74°F
- Early September (1st–15th)
- 38%
- Late September (16th–end)
- 24%
- Rain frequency
- 32% of days
Park City
UT
- Clear days, September
- 30%
- Sample size
- n=240 days
- Avg high
- 70°F
- Early September (1st–15th)
- 41%
- Late September (16th–end)
- 19%
- Rain frequency
- 32% of days
Frequently asked
Is Boston or Park City warmer in September?
Boston runs warmer by day in September. Boston averages highs of 74°F (highs n=240 days); Park City averages highs of 70°F (highs n=240 days) (ERA5 2018–2025). Historical averages, not a forecast.
Does it rain more in Boston or Park City in September?
Days with measurable rain: Boston 32%, Park City 32% (n=240 and n=240 days). ERA5 2018–2025; historical, not a forecast.
Which is sunnier in September, Boston or Park City?
Essentially a tie in September: Boston is 31% clear historically, Park City is 30% clear (8-year ERA5 average) — within the noise. Avg high 74°F vs 70°F. Pick based on flight time or price, not weather — the weather won't decide this one for you.
Compare Boston vs Park City 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.