When does San Antonio typically see its first 100-degree day?

A shower a day keeps 100° away...


Ready or not, summer will be in full swing soon. While that typically means vacations and fun in the sun, it’s also when San Antonio experiences seemingly endless heat and dry spells.

But when, on average, does the mercury first reach 100°? Has the Alamo City ever experienced a summer without a 100-degree day? And how hot will Summer 2023 really be?

Average First 100-Degree Day

100° Climatology for San Antonio (Copyright 2023 by KSAT - All rights reserved.)

San Antonio’s average first 100-degree day occurs in late June. On June 26th to be precise. The earliest first 100-degree day was on February 21, 1996. The latest date that San Antonio saw 100° was just a couple of years ago — on September 6, 2021. However, since 1886 when records began, there have been 23 years in San Antonio when the thermometer never reached the 100-degree mark. 2007 was the last time for this to happen.

In contrast, San Antonio experienced the most 100-degree days in a year in 2009 with 59 triple-digit days. 2022 came in a close second with 58.

And take a look at this: the top 5 years with the most 100-degree days in San Antonio have all occurred in the last 15 years.

YearNumber of 100° Days
2020 (& 1998)36

Summer 2023 Forecast

While it will still definitely be hot in San Antonio over the summer of 2023, it will probably NOT be as hot as the 2022 summer.

And here’s why: South Central Texas is heading into summer with a rainy spring under our belt. Since March 1, San Antonio has seen more than 10 inches of beneficial rain. With the ground saturated, there will be more moisture in the air, preventing temperatures from easily soaring to 100° regularly. A nifty phrase I’ve coined for this phenomenon is “A shower a day keeps 100° away.” Cheesy, I know 😉

This doesn’t mean that we won’t reach 100° at all this season, just that it will be more difficult to see many, many triple-digit days. However, the downside of heading into summer with saturated grounds is that humidity *may* be higher than average. This means a higher heat index — or the “feels like” temperature.

As for rainfall, we can expect near-average precipitation. For June, that’s 3.28″. Average July rainfall is 2.41″, and in August it’s 2.15″.

Summer Curveballs

Summer is also when the Atlantic hurricane season ramps up. All it takes is one storm to bring flooding rains inland to San Antonio. In the same token — if we’re on the dry side of a tropical storm — this can make temperatures soar to well above 100 degrees.

Regardless of how this summer shakes out, you can count on your Weather Authority to bring you the latest. Stay cool, y’all!

About the Author:

Sarah Spivey is a San Antonio native who grew up watching KSAT. She has been a proud member of the KSAT Weather Authority Team since 2017. Sarah is a Clark High School and Texas A&M University graduate. She previously worked at KTEN News. When Sarah is not busy forecasting, she enjoys hanging out with her husband and cat, and playing music.