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SunnyDays

ERA5 almanac — 8 years of real data

Steamboat Springs in September

Steamboat Springs in September: 14% of days see measurable rain, 74°F average high, 52% of days historically clear (n=240, ERA5 2018–2025).

Steamboat Springs in September is a mixed month for sun: 52% of days historically clear (n=240, avg high 74°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 Steamboat Springs 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 Steamboat Springs 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		 64% n=120 74°F
Late September
16th–end		 39% n=120 74°F
Full month average 52% n=240 74°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 Steamboat Springs 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		 84% n=120
Late September
16th–end		 50% n=120
Full month average 67% n=240
11.9 h median sunshine per day 97% of days exceed 8 h sunshine 14% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 52%. Sunshine-based “warm & sunny”: 67%. The 15-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

Steamboat Springs in September is genuinely mixed: 52% of days historically clear (n=240), avg high 74°F — roughly even odds. The two halves differ materially (64% early, 39% 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 Steamboat Springs

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

Historical clear-sky % for Steamboat Springs, 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 0% n=240 All destinations →
May 4% n=248 All destinations →
June 45% n=240 All destinations →
July 64% n=248 All destinations →
August 62% n=248 All destinations →
September ← this page 52% n=240 All destinations →
October 5% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

Frequently asked

Does it rain in Steamboat Springs in September?

Rarely. Only 14% of days in Steamboat Springs see measurable rain in September, based on 8 years of ERA5 historical data (n=240 days, 2018–2025). This is a historical average, not a forecast.

Is Steamboat Springs good for sun in September?

It's mixed. Steamboat Springs in September is clear on 52% of days historically (avg high 74°F, n=240 days, ERA5 2018–2025) — the outcome varies year to year.

How Steamboat Springs compares in September

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Steamboat Springs 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.