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SunnyDays

ERA5 almanac — 8 years of real data

Moab in May

Historically one of the better months to visit Moab for sun: 73% of days are clear on average (n=248, avg high 81°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 Moab 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 Moab 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		 68% n=120 81°F
Late May
16th–end		 77% n=128 81°F
Full month average 73% n=248 81°F

Sunshine & warmth in May

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 Moab in May. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early May
1st–15th		 79% n=120
Late May
16th–end		 90% n=128
Full month average 85% n=248
13.7 h median sunshine per day 97% 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: 73%. Sunshine-based “warm & sunny”: 85%. 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

Moab clears solidly in May: 73% of days historically (n=248), avg high 81°F. Most trips here in May will find more sun than cloud.

Every month in Moab

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

Historical clear-sky % for Moab, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 4% n=248 All destinations →
April 46% n=240 All destinations →
May ← this page 73% n=248 All destinations →
June 88% n=240 All destinations →
July 90% n=248 All destinations →
August 84% n=248 All destinations →
September 84% n=240 All destinations →
October 41% n=248 All destinations →
November 2% n=240 All destinations →
December 0% 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.