Temps to hit 90, but when is 100 coming?

The average high temperature in San Antonio on March 5 is a comfortable 71 degrees. However, it’s rare for temperatures to actually be “average” this time of the year. During early March, high temps are capable of rising into the 90s, and lows are capable of dropping below freezing. Basically, anything can happen this time of the year.

Right now, San Antonio is experiencing the warm part of the early March temperature spectrum. Afternoon temperatures Tuesday reached 90 degrees for the first time in 2024. But when can we expect the first 100-degree day?

The average date

If you purely look at the average, San Antonio is still several months away from reaching 100 degrees. Over the past 100 years of weather records, the average date of the first 100-degree day does not arrive until the end of June — June 30 to be exact.

If we analyze a more recent period — say, since 1990, as the effects of climate change have become more apparent — the average date of the first occurrence of triple-digit temperatures comes June 26. So while the onset of triple-digit heat has arrived slightly earlier in recent years, it’s still more than three months away, on average.

It can be earlier

Those are just the averages. If you’ve lived in Texas long enough, you know that Texas weather doesn’t like to follow the rules very often.

In many cases, tripledigit temperatures have arrived in the Alamo City much earlier in the year, sometimes in early to mid-spring. For instance, the first 100-degree day of the year has come by the end of April six times in the past 100 years.

The earliest occurrence of 100-degree weather in San Antonio actually happened in February, when temperatures hit the century mark on Feb. 21, 1996.

Best odds after May

The odds of reaching 100 degrees have become a bit more favorable in May. History tells us that San Antonio temperatures have a nearly 20% chance of touching triple digits by the end of May. Of course, the odds of reaching triple digits continue to increase as we move into June, July and August. That’s when high atmospheric pressure typically dominates the forecast in the Lone Star State.

This year, it’s certainly possible San Antonio could reach 100 degrees during March, April or May, but the odds tell us that we still have a few months to enjoy spring. Then, the heat will really set in by June.

Sometimes never

It sounds crazy that San Antonio would go through an entire summer without reaching 100 degrees, but it does happen from time to time. In fact, it has happened 14 times in the past 100 years. The last time it occurred was in 2007. During that summer, San Antonio topped out at 98 degrees and only reached the 95-degree mark a total of four times.