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SunnyDays

ERA5 almanac — 8 years of real data

San Antonio in March

San Antonio in March is historically a poor month for sun: only 33% of days clear across 8 years (n=248, avg high 78°F). 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 San Antonio 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 March

Clear-sky percentage for San Antonio in March, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early March
1st–15th		 32% n=120 78°F
Late March
16th–end		 33% n=128 78°F
Full month average 33% n=248 78°F

Sunshine & warmth in March

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 San Antonio in March. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early March
1st–15th		 52% n=120
Late March
16th–end		 62% n=128
Full month average 57% n=248
9.0 h median sunshine per day 57% of days exceed 8 h sunshine 32% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 33%. Sunshine-based “warm & sunny”: 57%. The 24-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

San Antonio is mostly overcast in March historically: only 33% of days are clear across 8 years (n=248), avg high 78°F. Most visitors this month will see more clouds than sun.

Every month in San Antonio

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

Historical clear-sky % for San Antonio, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 10% n=248 All destinations →
February 19% n=226 All destinations →
March ← this page 33% n=248 All destinations →
April 36% n=240 All destinations →
May 26% n=248 All destinations →
June 31% n=240 All destinations →
July 44% n=248 All destinations →
August 45% n=248 All destinations →
September 36% n=240 All destinations →
October 49% n=248 All destinations →
November 33% n=240 All destinations →
December 17% 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.