ST. LOUIS - A heat advisory remains in effect through Thursday evening, June 26, 2025, for the Alton area and the Metro East region, following a heat warning that lasted until Monday night, June 23, 2025, according to National Weather Service in St. Louis meteorologist Brad Charboneau.
Residents can expect heat indexes ranging from the upper 90s to 105 degrees Tuesday through Thursday, he said.
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The forecasted high for Monday is 95 degrees with a low of 77 degrees overnight, then a high of 95 is predicted for Tuesday and 94 degrees on Wednesday. Thursday is again predicted to have a high near 95 degrees. On Friday, a high of 93 degrees is predicted, so the weather will be a repeat nearly every day this week.
Charboneau said the persistent heat is due to a high-pressure system settled over the Ohio Valley, creating a stationary dome of heat typical for summer months. This system, combined with significant humidity and limited air flow, is causing hot and humid conditions to continue for several days, he said.
"Even though we don’t have a heat warning for the coming days, it is an advisory starting Tuesday," Charboneau said. "We advise those spending a lot of time outdoors to avoid direct sun exposure as much as possible, take frequent breaks, stay hydrated, and be attentive to their bodies."
Charboneau said temperatures are forecasted to gradually decline starting Friday, with showers and thunderstorms anticipated late in the week through the weekend, which may provide some relief.
No major cold fronts are expected in the near future, Charboneau added.
