This week, the main weather story in South Texas will be the consistent extreme heat — and rightfully so, because high temperatures will be in the upper 90s and low 100s every day, and heat index values, or “feels like” temperatures that factor in humidity, will be close to 110 degrees for many.

However, a weak atmospheric disturbance is likely to offer some slight relief from the heat on Wednesday, and it may bring a slight chance of rain to the region as well. Storms likely will be isolated, meaning the majority of areas will stay dry. However, a few storms could become strong, capable of large hail. Here’s when the best storm chances will be.

Storm chances

Wednesday morning, a cluster of thunderstorms moved throughout parts of Central and Southeast Texas, from Waco down to Houston. While these storms have stayed north and east of the San Antonio area, they may create outflow boundaries, or slight atmospheric disturbances, that could bring cooler air and slight rain chances to the Alamo City by the middle of the day.

As of 11 a.m. Wednesday, an outflow boundary had already passed through New Braunfels, and it caused temperatures to drop to 73 degrees in the city. The boundary is likely to bring slightly cooler air into San Antonio by noon, possibly dropping temps into the upper 70s to low 80s briefly.

The boundary may also being a few light showers, but rainfall is expected to be very light through the middle of the day. By the late afternoon, a few isolated thunderstorms may form along the stalled boundary, mainly between 4 and 8 p.m.

Storms are not expected to be widespread. In fact, no more than 10% or 20% of South Texas will even see rain. However, the storms that do develop could produce hail and damaging wind gusts. While the overall severe weather threat is low, it’s not zero.

Hot temperatures return

Morning temperatures have been very warm throughout San Antonio, hovering in the 80s under mostly cloudy skies. Temperatures will likely drop several degrees just before noon, as the aforementioned outflow boundary moves into San Antonio.

Enjoy the break from the heat while we have it. Temperatures are expected to rebound by the late afternoon as the sun breaks through the clouds. Still, high temperatures will likely stay a bit cooler than previously expected, reaching the mid-90s by the late afternoon. 

While actual temperatures will stay in the 90s for many, it will continue to feel much hotter. Heat index values will rise well into the triple digits during the afternoon and early evening. If you have to be outside, be sure to stay properly hydrated and take breaks away from the sun.

Over the next several days, extreme heat is expected to continue across South Texas. By Thursday, high temperatures are expected to reach close to 100 degrees in San Antonio. Highs in the upper 90s to low 100s are also expected Friday and into the weekend.

Long-range models are showing a potential weak cold front moving through Texas by late Monday or Tuesday next week. While the front won’t make things “cold” per se, it could provide some relief from the heat and bring temperatures closer to average for early to mid-June.