Ready or not, South Central Texas summer is officially kicking into high gear.
San Antonio recorded its first 100-degree day of the year Wednesday, reaching the triple-digit mark later than we typically do.
On average, San Antonio’s first 100° day occurs around June 26. This year, however, the city managed to make it well into July before finally hitting the century mark.
The latest first 100° day on record came in September 2021. Meanwhile, there have been 23 years, since records began in 1886, when the city never reached 100° — most recently in 2007.
Why did it take so long?
The biggest reason: moisture.
Spring and early summer brought frequent rounds of rain across South Central Texas, leaving soils much wetter than normal. When the ground contains plenty of moisture, a portion of the sun’s energy goes toward evaporating water rather than heating the air.
This process is called evaporative cooling, and it can keep afternoon temperatures several degrees below their full potential.
The lush vegetation the area has seen this year has also helped. Plants release moisture into the atmosphere through a process called transpiration, which adds another layer of natural cooling. As a result, many afternoons that may have otherwise reached 100° topped out in the mid-to-upper 90s instead.
Even though temperatures stayed below 100°, it hasn’t exactly been comfortable. The same moisture that helped keep the thermometer in check also boosted humidity levels. That has pushed heat index values, also known as the “feels-like” temperature, well above 100° on many days.
What’s next?
Now that the hottest part of the summer nears, triple-digit temperatures are likely to become more common. As the ground gradually dries out, less energy will be used for evaporation and more will go directly into heating the air.
In other words, the inevitable has been delayed, but summer’s hottest stretch is still to come.
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