Corn-sweat and heat impact high school sports practice

ST. LOUIS — The area is in a stretch of late summer heat that is going to feel even worse after the fall-like temperatures of last week. Temperatures today will heat up into the mid-upper 90s with top heat index values soaring to near 105. You can attribute the return of humidity to both the return of southerly winds and something called “corn-sweat,” or the off-gassing of humidity from the lush corn crops of Iowa, Missouri and Illinois. No matter the source, it is going to be steamy for the next couple of days.

The heat and humidity will have an impact on our local fall high school sports activities. They use something called the Wet Bulb Globe Temperature or WBGT to determine their level of activity. The major difference between the WBGT and the commonly used heat index is that the WBGT takes into account the impact of direct sunlight along with high temperatures, humidity, wind speed, sun angle and cloud cover. These can be measured using an instrument called the wet bulb globe and the “temperature” readings look significantly different from the heat index.

Monday’s forecast max WBGT is between 84 and 85 in metropolitan St. Louis. That translates to a maximum practice time of two hours with 20 minute breaks within each hour of practice.

This heat wave will peak Tuesday, with daytime temperatures very close to 100 and possibly a little over in St. Louis City. Relief will come with a cold front late in the week that will also include much needed rain from thunderstorms.

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