An immense ridge of high pressure over the Central Plains and Mississippi Valley entrenched heat and high dewpoint air across the region, resulting in daily heat indices from 100 to around 120, with very little recovery during the overnight hours. One direct fatality occurred when an infant was left in a vehicle for an extended period of time during the day in Yankton.

Excessive Heat in HUTCHINSON, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 100 to 118 degrees with a maximum heat index of 118 degrees at a South Dakota State University Mesonet site in Parkston on August 21, 114 degrees at a South Dakota Road Weather Information System site near Freeman on August 23, and 111 degrees near Tripp on August 21.

Excessive Heat in BON HOMME, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 100 to 111 degrees with a maximum heat index of 111 degrees at a South Dakota Road Weather Information System site near Tyndall on August 22.

Excessive Heat in LINCOLN, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: AWOS

Daily afternoon and evening heat indices ranged from 100 to 118 degrees with a maximum heat index of 118 degrees at an Automated Weather Observing System site at Tea on August 22 and 23, 114 degrees at a personal weather station near Canton on August 21, and 112 degrees at a South Dakota Road Weather Information System site near Davis on August 21.

Excessive Heat in CLAY, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 100 to 115 degrees with a maximum heat index of 115 degrees at a South Dakota State University Mesonet site near Beresford and 113 degrees at an Automated Weather Observing System site near Vermillion on August 21.

Excessive Heat in BEADLE, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: ASOS

Daily afternoon and evening heat indices ranged from 100 to 113 degrees with a maximum heat index of 113 degrees at the South Dakota Road Weather Information System site near Cavour and 111 degrees at Automated Surface Observing System site KHON near Huron on August 21.

Excessive Heat in JERAULD, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 105 to 116 degrees with a maximum heat index of 116 degrees at the South Dakota Road Weather Information System site near Lane on August 21.

Excessive Heat in YANKTON, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: AWOS

Daily afternoon and evening heat indices ranged from 100 to 115 degrees with a maximum heat index of 115 degrees at Automated Weather Observing System site KYKN at Yankton on August 21.  A direct fatality occurred in Yankton on the third day of excessive heat when a child was left in a vehicle for an extended time. At the time of the incident, the heat index was 112 degrees with an air temperature of 100 degrees.

Excessive Heat in KINGSBURY, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 100 to 112 degrees with a maximum heat index of 112 degrees at the South Dakota Road Weather Information System site near Arlington on August 22.

Excessive Heat in MINNEHAHA, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 100 to 118 degrees with a maximum heat index of 118 degrees at a South Dakota State University Mesonet site near Baltic on August 23, 116 degrees at personal weather stations in Sioux Falls and near Baltic on August 21 and 23, 115 degrees at a South Dakota State University site near Wall Lake on August 23, and 110 degrees at Automated Surface Observing System site KFSD at Sioux Falls on August 21 and 22.

Excessive Heat in LAKE, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: AWOS

Daily afternoon and evening heat indices ranged from 105 to 110 degrees with a maximum heat index of 111 degrees at Automated Weather Observing System site KMDS  on August 21.

Excessive Heat in MOODY, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 105 to 110 degrees with a maximum heat index of 110 degrees at Automated Weather Observing System site K4P3 near Flandreau on August 23 and 108 degrees at a South Dakota State University Mesonet site near Flandreau on August 21.

Excessive Heat in AURORA, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 105 to 111 degrees with a maximum heat index of 111 degrees at a Road Weather Information System site near Plankinton and 110 degrees at a South Dakota State University Mesonet site at White Lake on August 21.

Excessive Heat in DAVISON, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: ASOS

Daily afternoon and evening heat indices ranged from 105 to 113 degrees with a maximum heat index of 113 degrees at a personal weather station in Ethan and 112 degrees at Automated Surface Observing System site KMHE near Mitchell on August 23.

Excessive Heat in HANSON, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: ASOS

Daily afternoon and evening heat indices ranged from 110 to 122 degrees with a maximum heat index of 122 degrees at a South Dakota Road Weather Information System site near Alexandria on August 23.

Excessive Heat in CHARLES MIX, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: AWOS

Daily afternoon and evening heat indices ranged from 105 to 118 degrees with a maximum heat index of 118 degrees at an Automated Weather Observing System site at Wagner on August 21, 114 degrees at a personal weather station in Platte on August 21 and 22, and 109 degrees at a South Dakota Road Weather Information System site near Wagner on August 21.

Excessive Heat in DOUGLAS, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 100 to 108 degrees with a maximum heat index of 108 degrees at a South Dakota Road Weather Information System site near Corsica on August 21.

Excessive Heat in TURNER, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 102 to 123 degrees with a maximum heat index of 123 degrees at a personal weather station near Centerville and at a South Dakota Road Weather Information System site near Irene on August 23.

Excessive Heat in BROOKINGS, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 100 to 110 degrees with a maximum heat index of 110 degrees at a personal weather station in Elkton on August 23, and 109 degrees at South Dakota State University Mesonet sites near Astoria and Volga on August 21-22.

Excessive Heat in SANBORN, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 105 to 115 degrees with a maximum heat index of 115 degrees at a South Dakota State University Mesonet site near Letcher and 114 degrees at a South Dakota Road Weather Information System site near Forestburg on August 21.

Excessive Heat in MCCOOK, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 109 to 121 degrees with a maximum heat index of 121 degrees at a personal weather station near Canova on August 23, 115 degrees at a South Dakota Road Weather Information System site near Dolton on August 21, and 111 degrees at a South Dakota Road Weather Information System site near Montrose on both August 21 and 23.

Excessive Heat in GREGORY, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Mesonet

Daily afternoon and evening heat indices ranged from 100 to 112 degrees with a maximum heat index of 112 degrees at a personal weather station near Bonesteel and 108 degrees at a site near Fairfax, and 107 degrees at a South Dakota Road Weather Information site near Pickstown on August 23.

Excessive Heat in MINER, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 105 to 111 degrees with a maximum heat index of 111 degrees at the South Dakota Road Weather Information System site near Howard on August 21.

Excessive Heat in BRULE, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 23-AUG-23 21:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 100 to 107 degrees with a maximum heat index of 107 degrees at South Dakota Road Weather Information System site near Kimball on August 23 and Automated Weather Observing System site K9V9 at Chamberlain on August 21-22.

Excessive Heat in UNION, SOUTH DAKOTA
From 21-AUG-23 11:00:00 to 24-AUG-23 18:00:00 (CST-6)
Reported by: Department of Highways

Daily afternoon and evening heat indices ranged from 100 to 119 degrees with a maximum heat index of 119 degrees at a South Dakota Road Weather Information System site near North Sioux City on August 21 and 112 degrees near Beresford on August 23.