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SunnyDays

ERA5 almanac — 8 years of real data

Santa Fe in September

Santa Fe in September is a mixed month for sun: 50% of days historically clear (n=240, avg high 76°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 Santa Fe 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 Santa Fe 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		 50% n=120 76°F
Late September
16th–end		 50% n=120 76°F
Full month average 50% n=240 76°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 Santa Fe 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		 71% n=120
Full month average 78% n=240
11.9 h median sunshine per day 97% of days exceed 8 h sunshine 16% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 50%. Sunshine-based “warm & sunny”: 78%. The 28-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

Santa Fe in September is genuinely mixed: 50% of days historically clear (n=240), avg high 76°F — roughly even odds. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Santa Fe

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

Historical clear-sky % for Santa Fe, 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 8% n=240 All destinations →
May 41% n=248 All destinations →
June 58% n=240 All destinations →
July 41% n=248 All destinations →
August 47% n=248 All destinations →
September ← this page 50% n=240 All destinations →
October 14% n=248 All destinations →
November 0% n=240 All destinations →
December 0% n=248 All destinations →

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.