Dangerous heat today, then a threat for storms Friday into Saturday

Heat index values will peak this afternoon near 110°

Justin Horne, KSAT Weather Authority Meteorologist

Published: June 18, 2026 at 4:51 AM

FORECAST HIGHLIGHTS

DANGEROUS HEAT TODAY: 90s + thick humidity = heat index values near 110°
STORMS LATE FRIDAY?: Possible, will depend on storms to our north
SATURDAY: Threat for a few storms continues, cooler

FORECAST

HEAT INDEX TO SOAR TODAY

After brief bout of morning cloud cover, full afternoon sunshine will help to push temperatures into the upper-90s. Meantime, the humidity will be especially thick today. This will allow heat index values to top 100° as soon as the noon hour. By peak heating, ‘feels like’ temperatures could reach 110°, if not a bit higher. Excessive Heat Warnings are in effect today.

FRIDAY

Pre-dawn on Friday, a few storms may try to work into the area from the northwest. At this time, we expect this activity to stay north of San Antonio.

Temperatures will cool slightly tomorrow thanks to added cloud cover. That said, it’ll still be hot and humid, and heat index values may still jump above 100°. Outflow boundaries from storms to our north may help to fire storms Friday evening and Friday night. In this type of setup, these random outflow boundaries will be the deciding factor as to where storms develop.

SATURDAY

Rain chances continue into Saturday, but like Friday, the distribution of storms will depend on outflow boundaries. Odds currently sit at 50% through Saturday afternoon. It won’t be raining all day, but some could see heavy rainfall.

Quieter weather is expected Sunday for Father’s Day.