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SunnyDays

ERA5 almanac — 8 years of real data

Austin in May

Austin in May is historically a poor month for sun: only 27% of days clear across 8 years (n=248, avg high 87°F). October is the clearest month for Austin historically. 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 Austin 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 Austin 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		 32% n=120 87°F
Late May
16th–end		 23% n=128 87°F
Full month average 27% n=248 87°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 Austin 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		 74% n=120
Late May
16th–end		 91% n=128
Full month average 83% n=248
10.6 h median sunshine per day 75% of days exceed 8 h sunshine 49% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 27%. Sunshine-based “warm & sunny”: 83%. The 56-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

Austin is mostly overcast in May historically: only 27% of days are clear across 8 years (n=248), avg high 87°F. If you want sun in Austin, October is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in October — historically the best month for sun in Austin.

Every month in Austin

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

Historical clear-sky % for Austin, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 4% n=248 All destinations →
February 15% n=226 All destinations →
March 26% n=248 All destinations →
April 35% n=240 All destinations →
May ← this page 27% n=248 All destinations →
June 32% n=240 All destinations →
July 47% n=248 All destinations →
August 46% n=248 All destinations →
September 41% n=240 All destinations →
October 48% n=248 All destinations →
November 25% n=240 All destinations →
December 11% 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.