Weather
St. Louis Heat Index Could Reach 107 Tuesday
St. Louis, Missouri – Summer like heat returns Tuesday, with the St. Louis heat index near 107 and stronger thunderstorms possible north of Interstate 70.
By Natalie Rhodes · 2026-09-14T11:45:02.695Z
St. Louis, Missouri – Summer like heat returns Tuesday, with the St. Louis heat index near 107 and stronger thunderstorms possible north of Interstate 70.
According to the National Weather Service in St. Louis, heat and humidity will build across much of the region Tuesday. Storms and cloud cover north of I 70 could limit temperatures there, while areas farther south face greater heat.
The Tuesday heat index could reach 107 in St. Louis and Hermann, 106 in Hillsboro and 105 around Troy, Vandalia and Steeleville. Some locations farther south could feel even hotter, with heat index values around 109 near Farmington and Centerville.
Thunderstorms provide another concern Tuesday afternoon. Storm chances reach 60% to 80% north of I 70, where an isolated damaging wind threat exists. The Weather Service says a few stronger thunderstorms are possible.
Residents should account for the combination of heat, humidity and thunderstorms when making Tuesday plans. People spending extended periods outdoors should limit heat exposure when possible and monitor conditions, particularly north of I 70 where storms are more likely.
Hot conditions could continue Wednesday, although uncertainty remains north of I 70 because of clouds and thunderstorms. Wednesday's heat index could reach about 105 in St. Louis and Hermann and 104 around Hillsboro.
The Weather Service says the unseasonable heat is more likely across southeast Missouri and southern Illinois, with a 60% to 80% chance there. Storm chances Wednesday are 40% to 60% across northern Missouri, but severe weather is considered unlikely.
Tuesday brings the more immediate combination of dangerous heat and stronger storm potential, particularly during the afternoon.