Summary of Aug 31 - Sep 5, 2026 heatwave

Heat Index

The graphics below display the observed heat index from ASOS/AWOS (airports) stations across our region from August 31-September 5. Most locations registered heat index readings near or above 105 degrees for 5 consecutive days. A few locations reached or exceeded 110 degrees by the 4th and 5th. 4 of our 5 long term climate stations broke their all-time highest September heat index during this heat wave. Cape Girardeau registered 14 hours with a heat index at or above 105 degrees during this heatwave. In comparison, from 1996 to 2025 they only reached 105 for 1 hour total during the month of September. Poplar Bluff spent 20 hours with a heat index of at least 105 degrees compared to a total of 13 hours spent at or above that threshold from 1997 through 2025 during the month of September.

Peak Heat Index: August 31, 2026	Peak Heat Index: September 1, 2026

Peak Heat Index: September 2, 2026	Peak Heat Index: September 3, 2026

Peak Heat Index: September 4, 2026	Peak Heat Index: September 5, 2026

The maps below show the peak heat index from the Kentucky mesonet stations each day during this heatwave:

Peak Heat Index: August 31, 2026	Peak Heat Index: September 1, 2026

Peak Heat Index: September 2, 2026	Peak Heat Index: September 3, 2026

Peak Heat Index: September 4, 2026	Peak Heat Index: September 5, 2026

High Temperatures

High temperatures ranged from the mid 90s to low 100s during this heatwave. Mount Vernon, IL hit 100 degrees on 5 consecutive days. Evansville reached at least 98 degrees on 5 consecutive days which was their longest such streak in the month of September since 1925 (7 days then)! Paducah exceeded 95 degrees for 5 consecutive days, which was the first time we had a streak that long in the month of September since 2002 (6 days then). High temperatures reached 100 degrees across the entire region on September 5th, with many of these readings being the warmest in the month of September since 1954. A few locations reached their warmest temperatures for any time of the year since 2012.

High Temperatures: August 31, 2026	High Temperatures: September 1, 2026

High Temperatures: September 2, 2026	High Temperatures: September 3, 2026

High Temperatures: September 4, 2026	High Temperatures: September 5, 2026

Stats/Records

4 of our 5 climate stations broke their all-time highest September heat index as shown in the table below. Many locations also registered their warmest September temperature since 1954. In the case of Cape Girardeau they set their all-time highest September temperature, since records only date back to 1960 there. Unseasonably high humidity levels were also present during this heatwave, with most locations reaching dew points into the mid to upper 70s. Paducah registered 4 consecutive days with a dew point above 75 degrees which broke the previous September record of 3 consecutive days set back on September 9-11, 1991.

Environment

An unseasonably strong upper level ridge set up over us on August 31st and remained in place through September 5th. A backdoor cold front moved southwest through the region during the day on the 6th. Relief didn't reach southern portions of southeast Missouri and far west Kentucky until the evening of the 6th.

Aug 31 - 7 PM CDT	Sep 2 - 1 PM CDT	Sep 4 - 7 PM CDT	Sep 5 - 7 PM CDT

Map showing all of the National Weather Service Watches, Warnings, and Advisories that were in effect the afternoon of September 3rd. The magenta color shows where the Extreme Heat Warnings were in effect on this date.