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SunnyDays

ERA5 almanac — 8 years of real data

Missoula in August

Missoula in August: 11% of days see measurable rain, 86°F average high, 74% of days historically clear (n=248, ERA5 2018–2025).

Historically one of the better months to visit Missoula for sun: 74% of days are clear on average (n=248, avg high 86°F). Every percentage here is a historical average from 8 years of ERA5 data — 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 Missoula 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 August

Clear-sky percentage for Missoula in August, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early August
1st–15th		 77% n=120 86°F
Late August
16th–end		 72% n=128 86°F
Full month average 74% n=248 86°F

Sunshine & warmth in August

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for Missoula in August. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early August
1st–15th		 95% n=120
Late August
16th–end		 89% n=128
Full month average 92% n=248
13.3 h median sunshine per day 93% of days exceed 8 h sunshine 11% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 74%. Sunshine-based “warm & sunny”: 92%. The 18-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

Missoula clears solidly in August: 74% of days historically (n=248), avg high 86°F. Most trips here in August will find more sun than cloud.

Every month in Missoula

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

Historical clear-sky % for Missoula, 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 4% n=240 All destinations →
May 22% n=248 All destinations →
June 44% n=240 All destinations →
July 82% n=248 All destinations →
August ← this page 74% n=248 All destinations →
September 57% n=240 All destinations →
October 14% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Missoula in August?

Rarely. Only 11% of days in Missoula see measurable rain in August, based on 8 years of ERA5 historical data (n=248 days, 2018–2025). This is a historical average, not a forecast.

Is Missoula good for sun in August?

Yes. Missoula is historically strong for sun in August: 74% of days are clear on average (avg high 86°F, n=248 days, ERA5 2018–2025).

How Missoula compares in August

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Missoula this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

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.