Belleville to see heat index over 100 + risk of severe thunderstorms. See timing
Belleville residents can expect a heat index as high as 103 degrees Fahrenheit Wednesday, as well as potential for severe thunderstorms later in the week. The high air temperature expected in Belleville Wednesday is around 95 degrees.
While Wednesday is expected to be hot in the metro-east, it shouldn’t be quite as warm as Tuesday’s heat index of around 106, Matt Beitscher, lead meteorologist with the National Weather Service St. Louis office, told the News-Democrat Wednesday morning.
The term heat index refers to “what the temperature feels like to the human body” considering relative humidity combined with the air temperature, according to the NWS.
Heat index values do not consider sunlight, sun angle or wind speed, Beitscher said, and the heat index more accurately conveys how someone in the shade would feel.
“If you’re out in unfiltered sunshine, it’s going to feel quite a bit worse than the heat index is going to suggest,” Beitscher said.
Forecasters expect heat to continue into Thursday, with a high temperature of 95 degrees in Belleville and a heat index of 106.
Heat safety tips
It’s important to stay hydrated when it’s hot out, Beitscher said, and it’s a good idea to avoid spending time in direct sunlight when possible.
“The most important thing with any kind of heat-related illness or situation is to pay attention to the signs that your body is exhibiting,” Beitscher said.
If you’re sweating profusely and starting to get dizzy, that could indicate the onset of heat exhaustion, he said. And if you stop sweating and feel very dizzy with a pounding headache, you could have heat stroke.
It’s abnormal for the metro-east to see heat index values so high in early June, Beitscher added, but it’s not unprecedented.
When are severe storms possible?
The metro-east and greater St. Louis region have a “slight risk” of severe thunderstorms Thursday, the NWS reports. The period of greatest risk in St. Clair County is expected to be after 10 p.m. Thursday.
Areas north of St. Clair County, including Jersey County and farther north, are at an “enhanced risk” of severe thunderstorms Thursday.
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This story was originally published June 10, 2026 at 11:44 AM.
