Heat in Sanborn, South Dakota

Heat index values peaked during the afternoon hours of July 22 as high as 101 degrees at South Dakota Mesonet site LCMS2 2 miles east-northeast of Letcher and 100 degrees at South Dakota Mesonet site WSMS2 4 miles north-northwest of Woonsocket.

Moisture pooled in the vicinity of a nearly stationary boundary early on July 21, which slowly worked northward as a warm front over the next two days while a large upper level ridge expanded across the Northern Plains. Most areas experienced heat index values from 100 to 115 degrees, with the most consistent and highest heat index values on the afternoon of July 23 across far southeast South Dakota, northwest Iowa, and northeast Nebraska.