Heat in Lake, South Dakota

Dangerous heat index readings reached a brief afternoon peak as high as 108 degrees near Madison, 106 degrees at Wentworth, and 102 degrees 6 miles south of Madison.

A large high pressure system parked over the Mississippi River Valley, bringing several days of hot, southerly flow across the region. From the afternoon of June 28 to the evening of June 29, the combination of heat and humidity, boosted by recent rain, created dangerous conditions. Some heat index values exceeded 105 to 110 degrees in and near northwest Iowa.