Heat Index Records Shattered in September
Heat Index Records Shattered in September
US · Published Sep 23, 2026
• September has seen unprecedented heat index records in parts of the United States, with several weather stations reporting a significant increase in the number of hours with heat index values exceeding 100°F (37.8°C). The Paducah, Kentucky, National Weather Service office recorded over 70 hours of 100°F+ heat index, more than double the previous record. Similarly, the St. Louis office reported 57 hours of such conditions, surpassing the previous record of 32 hours set in
• Illinois State Climatologist Trent Ford noted that the first 21 days of September have been marked by unusually high humidity, contributing to these extreme conditions. However, fall-like weather has now arrived in Illinois, with temperatures dropping into the 70s°F (21-26°C) in southern Illinois and the 60s°F (15-20°C) in northern Illinois.

Impact & Risks

The prolonged periods of high heat index values pose significant health risks, particularly for vulnerable populations such as the elderly, children, and those with pre-existing health conditions. Extended exposure to such conditions can lead to heat-related illnesses, including heat exhaustion and heatstroke. The high humidity levels exacerbate the situation, making it harder for the body to cool down. These conditions also strain energy resources due to increased air conditioning use and can impact outdoor activities and labor.

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