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SunnyDays

ERA5 almanac — 8 years of real data

Coeur d'Alene in September

Coeur d'Alene in September: 20% of days see measurable rain, 75°F average high, 50% of days historically clear (n=240, ERA5 2018–2025).

Coeur d'Alene in September is a mixed month for sun: 50% of days historically clear (n=240, avg high 75°F). The outcome varies year to year — check the early/late split below. 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 Coeur d'Alene 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 Coeur d'Alene 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		 68% n=120 75°F
Late September
16th–end		 33% n=120 75°F
Full month average 50% n=240 75°F

Sunshine & warmth in September

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 Coeur d'Alene in September. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early September
1st–15th		 78% n=120
Late September
16th–end		 38% n=120
Full month average 58% n=240
11.4 h median sunshine per day 83% of days exceed 8 h sunshine 20% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 50%. Sunshine-based “warm & sunny”: 58%.

Bottom line

Coeur d'Alene in September is genuinely mixed: 50% of days historically clear (n=240), avg high 75°F — roughly even odds. The two halves differ materially (68% early, 33% late) — favour the early half of the month. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Coeur d'Alene

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

Historical clear-sky % for Coeur d'Alene, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 1% n=248 All destinations →
April 2% n=240 All destinations →
May 20% n=248 All destinations →
June 44% n=240 All destinations →
July 82% n=248 All destinations →
August 75% n=248 All destinations →
September ← this page 50% n=240 All destinations →
October 10% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Coeur d'Alene in September?

Sometimes. Coeur d'Alene sees measurable rain on 20% of days in September historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Coeur d'Alene good for sun in September?

It's mixed. Coeur d'Alene in September is clear on 50% of days historically (avg high 75°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.