San Antonio still hasn’t hit 100 degrees this summer. An expert explains why.

Here we are halfway through July, and extraordinary things are happening in San Antonio. People are still wearing pants, lawns are still green, and it’s possible to sit outside at happy hour (mosquitoes notwithstanding).

It’s summer in Texas, and San Antonio hasn’t recorded one official 100-degree day. According to one expert, that’s somewhat unusual.

“Typically San Antonio see its first 100-degree day by late June, on average. We haven’t seen one yet,” says Keith White, metrologist with the National Weather Service.

Using data from the San Antonio International Airport, daytime highs have averaged 89.7 degrees this year, far below the normal 93.5 degrees. This makes 2021 the 15th coolest year on record thus far based on NWS data going back 137 years.

While daytime temps have stayed relatively mild, nighttime temps have actually ticked upward. Morning lows are averaging 73.8 degrees, making it the 25th warmest year on record. San Antonio’s average temperature, a combination of both daytime and nighttime highs, clocks in at 81.8 degrees this year, the 43rd coolest year on record.

“This spring and most of the winter was year-to-above average. It was drier and warm through April, most of March, but on the 27th of April, we sort of hit a switch,” says White. “We’ve had some warmer days. But generally it’s been cooler, wetter.”

So what’s causing this cooling trend? White says that typically by this time of year, a big dome of high pressure usually hovers over the lower half of North America causing the beating sun and blazing temps we’ve come to expect. This year, that dome has shifted northward to areas like the Pacific Northwest and East Coast, causing deadly heat waves in unusual parts of the country.

It’s not quite time to break out the down parka, though. In June, the Alamo City did hit 99 degrees a handful of times, so those 100-degree days will likely return before the summer is through.

“There have been years in the record where a 100-degree day happened real late,” says White, adding that in 2010, SAT didn’t record its first official 100-degree day until August 11.

“We can’t say for certain, but we can bet we’ll see a few 100-degree days over the next few weeks,” he says.