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SunnyDays

ERA5 almanac — 8 years of real data

Key West in October

Key West in October is historically a poor month for sun: only 13% of days clear across 8 years (n=248, avg high 82°F). March is the clearest month for Key West historically. 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 Key West 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 October

Clear-sky percentage for Key West in October, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early October
1st–15th		 8% n=120 82°F
Late October
16th–end		 18% n=128 82°F
Full month average 13% n=248 82°F

Sunshine & warmth in October

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 Key West in October. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early October
1st–15th		 93% n=120
Late October
16th–end		 95% n=128
Full month average 94% n=248
10.9 h median sunshine per day 91% of days exceed 8 h sunshine 52% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 13%. Sunshine-based “warm & sunny”: 94%. The 81-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

Key West is a poor choice for sun in October: just 13% of days clear historically (n=248). March is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in March — historically the best month for sun in Key West.

Every month in Key West

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

Historical clear-sky % for Key West, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 27% n=248 All destinations →
February 37% n=226 All destinations →
March 45% n=248 All destinations →
April 44% n=240 All destinations →
May 33% n=248 All destinations →
June 14% n=240 All destinations →
July 17% n=248 All destinations →
August 13% n=248 All destinations →
September 11% n=240 All destinations →
October ← this page 13% n=248 All destinations →
November 30% n=240 All destinations →
December 41% 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.