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SunnyDays

ERA5 almanac — 8 years of real data

Whitefish in September

Whitefish in September: rain frequency data not yet backfilled for this month, 70°F average high, 38% of days historically clear (n=240, ERA5 2018–2025).

Whitefish in September is historically a poor month for sun: only 38% of days clear across 8 years (n=240, avg high 70°F). Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live Whitefish page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late September

Clear-sky percentage for Whitefish in September, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early September
1st–15th		 55% n=120 70°F
Late September
16th–end		 20% n=120 70°F
Full month average 38% n=240 70°F

Bottom line

Whitefish is mostly overcast in September historically: only 38% of days are clear across 8 years (n=240), avg high 70°F. The two halves differ materially (55% early, 20% late) — favour the early half of the month. Most visitors this month will see more clouds than sun.

Every month in Whitefish

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for Whitefish, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 0% n=248 All destinations →
April 1% n=240 All destinations →
May 14% n=248 All destinations →
June 32% n=240 All destinations →
July 71% n=248 All destinations →
August 66% n=248 All destinations →
September ← this page 38% n=240 All destinations →
October 1% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Is Whitefish good for sun in September?

It's mixed. Whitefish in September is clear on 38% of days historically (avg high 70°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

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.