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SunnyDays

ERA5 almanac — 8 years of real data

Phoenix in April

Historically one of the better months to visit Phoenix for sun: 94% of days are clear on average (n=240, avg high 88°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 Phoenix 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 Phoenix 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		 92% n=120 88°F
Late April
16th–end		 95% n=120 88°F
Full month average 94% n=240 88°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 Phoenix 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		 95% n=120
Late April
16th–end		 100% n=120
Full month average 98% n=240
12.8 h median sunshine per day 100% of days exceed 8 h sunshine 2% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 94%. Sunshine-based “warm & sunny”: 98%.

Bottom line

Phoenix is historically one of the best US destinations for sun in April: 94% of days meet the clear bar (avg high 88°F, n=240 days across 8 years). Pack for outdoor activity — this month consistently delivers.

Every month in Phoenix

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

Historical clear-sky % for Phoenix, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 17% n=248 All destinations →
February 41% n=226 All destinations →
March 61% n=248 All destinations →
April ← this page 94% n=240 All destinations →
May 95% n=248 All destinations →
June 94% n=240 All destinations →
July 76% n=248 All destinations →
August 76% n=248 All destinations →
September 82% n=240 All destinations →
October 85% n=248 All destinations →
November 63% n=240 All destinations →
December 22% 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.