Skip to main content
SunnyDays

ERA5 almanac — 8 years of real data

Tucson in May

Historically one of the better months to visit Tucson for sun: 94% of days are clear on average (n=248, avg high 92°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 May

Clear-sky percentage for Tucson in May, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early May
1st–15th		 94% n=120 92°F
Late May
16th–end		 94% n=128 92°F
Full month average 94% n=248 92°F

Bottom line

Tucson is historically one of the best US destinations for sun in May: 94% of days meet the clear bar (avg high 92°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 ← this page 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 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.