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SunnyDays

ERA5 almanac — 8 years of real data

Houston in October

Houston in October is a mixed month for sun: 44% of days historically clear (n=248, avg high 81°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 Houston 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 Houston 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		 53% n=120 81°F
Late October
16th–end		 35% n=128 81°F
Full month average 44% n=248 81°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 Houston 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		 88% n=120
Late October
16th–end		 65% n=128
Full month average 76% n=248
10.6 h median sunshine per day 77% of days exceed 8 h sunshine 35% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 44%. Sunshine-based “warm & sunny”: 76%. The 32-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

Houston in October is genuinely mixed: 44% of days historically clear (n=248), avg high 81°F — more cloudy than clear. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Houston

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

Historical clear-sky % for Houston, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 2% n=248 All destinations →
February 6% n=226 All destinations →
March 15% n=248 All destinations →
April 28% n=240 All destinations →
May 23% n=248 All destinations →
June 19% n=240 All destinations →
July 21% n=248 All destinations →
August 23% n=248 All destinations →
September 30% n=240 All destinations →
October ← this page 44% n=248 All destinations →
November 25% n=240 All destinations →
December 6% 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.