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SunnyDays

ERA5 almanac — 8 years of real data

Key West in April

Key West in April is a mixed month for sun: 44% of days historically clear (n=240, avg high 78°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 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 April

Clear-sky percentage for Key West in April, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early April
1st–15th		 51% n=120 78°F
Late April
16th–end		 38% n=120 78°F
Full month average 44% n=240 78°F

Sunshine & warmth in April

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 April. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early April
1st–15th		 98% n=120
Late April
16th–end		 100% n=120
Full month average 99% n=240
12.5 h median sunshine per day 98% of days exceed 8 h sunshine 21% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 44%. Sunshine-based “warm & sunny”: 99%. The 55-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 in April is genuinely mixed: 44% of days historically clear (n=240), avg high 78°F — more cloudy than clear. The outcome varies year to year; don't book if you need guaranteed sun.

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 ← this page 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 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.