A large upper level high pressure area built over the region bringing very hot and humid conditions.  This was the worst heat wave to hit the region since July 2006. Beginning on Friday July 15th and persisting through Wednesday July 20th, many locations experienced high temperatures in the 90s to lower 100s, with low temperatures in the 70s at night. In addition, humidity levels rose to extreme levels at times.  Surface dew point temperatures in the 70s and lower 80s brought extreme heat index values of up to 110 to 125 degrees.  The dewpoints were some of the highest ever recorded in the region. The dewpoint at Aberdeen tied the previous record with 82 degrees. Sisseton also tied their record with 83 degrees. Watertown came a degree shy of tying their record with 80 degrees.
The prolonged heat took its toll on livestock with fifteen hundred cattle perishing during the heat.  Numerous sports and outdoor activities were cancelled. Some of the highest heat index values included; 110 degrees at Mobridge; 111 degrees at Watertown; 113 degrees at Miller and Gettysburg; 114 degrees at Wheaton and Faulkton; 116 degrees at Pierre; 118 degrees at Sisseton; and 121 degrees at Aberdeen.  The highest heat index value occurred at Leola with a temperature of 98 degrees and a dewpoint of 82 degrees, the heat index hit 125 degrees.

Excessive Heat in WALWORTH, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in GRANT, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in CODINGTON, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in HAMLIN, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in DEUEL, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in POTTER, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in SULLY, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in HUGHES, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in LYMAN, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in MCPHERSON, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in EDMUNDS, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in FAULK, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in HYDE, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in HAND, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in BUFFALO, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in CORSON, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in DEWEY, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in BROWN, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in SPINK, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in STANLEY, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in JONES, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in MARSHALL, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in DAY, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in CLARK, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Excessive Heat in ROBERTS, SOUTH DAKOTA
From 16-JUL-11 12:00:00 to 20-JUL-11 15:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Excessive Heat in CAMPBELL, SOUTH DAKOTA
From 15-JUL-11 12:00:00 to 20-JUL-11 03:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet