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SunnyDays

ERA5 almanac — 8 years of real data

Tucson in October

Historically one of the better months to visit Tucson for sun: 82% of days are clear on average (n=248, avg high 86°F). Every percentage here is a historical average from 8 years of ERA5 data — 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 Tucson 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 Tucson 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		 78% n=120 86°F
Late October
16th–end		 85% n=128 86°F
Full month average 82% n=248 86°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 Tucson 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		 94% n=120
Late October
16th–end		 94% n=128
Full month average 94% n=248
10.9 h median sunshine per day 96% of days exceed 8 h sunshine 9% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 82%. Sunshine-based “warm & sunny”: 94%. The 12-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

Tucson is historically one of the best US destinations for sun in October: 82% of days meet the clear bar (avg high 86°F, n=248 days across 8 years). Pack for outdoor activity — this month consistently delivers.

Every month in Tucson

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

Historical clear-sky % for Tucson, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 13% n=248 All destinations →
February 38% n=226 All destinations →
March 57% n=248 All destinations →
April 88% n=240 All destinations →
May 94% n=248 All destinations →
June 89% n=240 All destinations →
July 57% n=248 All destinations →
August 55% n=248 All destinations →
September 70% n=240 All destinations →
October ← this page 82% n=248 All destinations →
November 56% n=240 All destinations →
December 27% 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.