Interesting Facts About the July 15-20th, 2011 Heatwave

The persistent heat wave over much of the central and northern U.S. came to an end on Wednesday (7/20) as a weak cold front moved across the area.  This cold front dropped temperatures back to near mid-July averages, and more importantly brought a much drier airmass into the region.  For an interesting visual animation of this heat wave over the U.S., click HERE.

Below are a several other interesting facts about this recent heat wave:

• This was the worst heat wave to affect central and northeastern South Dakota and west-central Minnesota since July 2006.  Beginning on Friday July 15th and persisting through Wednesday July 20th, many locations saw high temperatures rise into the 90s to low 100s, with low temperatures only falling into the 70s each night.
• In addition to the hot temperatures, humidity levels during this heat wave rose to extreme levels at times.  Surface dewpoint values were commonly in the mid-70s Fahrenheit, which most people percieve as uncomfortable.  However, at times dewpoint values soared into the 80-83F range, which when combined with temperatures in the 90s to near 100 F, lead to very oppressive heat indicies.
• Although not considered official weather records, the extremely high dewpoint temperatures recorded during this heat event were likely some of the highest values ever recorded in South Dakota.  Research is ongoing to verify this fact.  Below is summary of the highest dewpoint values recorded during this event:

   * Multiple cccurrences of this value.  The date/time of the last occurrence is noted.

•  Several locations experienced their first 100F readings of 2011 (see chart below).  In Aberdeen, this was the first time temperatures exceeded 100F since July 2007.       

A VERY HOT AND HUMID AIRMASS HAS BEEN STUCK OVER THE

DAKOTAS AND MINNESOTA. FOR MOST LOCATIONS HEAT INDEX

VALUES HAVE TOPPED 100 DEGREES WITH DEWPOINT READINGS

IN THE UPPER 70S AND LOW 80S. BELOW IS A LIST OF THE

HIGHEST HEAT INDEX VALUES RECORDED FOR SELECTED SITES

SUNDAY...MONDAY...TUESDAY

LOCATION                     SUNDAY HEAT INDEX

ABERDEEN ASOS                       120

SISSETON ASOS                       118

HURON RAWS                          117

DAKOTA LAKES RESEARCH FARM SDSU     115

MARSHALL COUNTY RAWS                115

SAND LAKE RAWS                      115

BIG STONE RAWS                      113

FAULKTON SDSU                       112

LEOLA SDSU                          112

FORT PIERRE RAWS                    111

WATERTOWN ASOS                      111

MOBRIDGE ASOS                       110

PIERRE ASOS                         109

SOUTH SHORE SDSU                    109

BEAR CREEK RAWS                     108

GETTYSBURG SDSU                     108

GRAND RIVER RAWS                    108

HIGHMORE SDSU                       106

ORTONVILLE AWOS                     106

WHEATON AWOS                        106

MCINTOSH SDSU                       105

TIMBER LAKE SDSU                    102

LOCATION                     MONDAY HEAT INDEX

DAKOTA LAKES RESEARCH FARM SDSU     116

ABERDEEN ASOS                       114

FAULKTON SDSU                       114

BIG STONE RAWS                      113

GETTYSBURG AWOS                     113

MILLER AWOS                         113

PIERRE ASOS                         113

HURON RAWS                          111

LAKE COCHRANE SDSU                  111

MILBANK AWOS                        111

HIGHMORE SDSU                       109

WATERTOWN ASOS                      109

BOWDLE SDSU                         107

GETTYSBURG SDSU                     107

BEAR CREEK RAWS                     106

FORT PIERRE RAWS                    106

MOBRIDGE ASOS                       106

ORTONVILLE AWOS                     106

SOUTH SHORE SDSU                    106

WHEATON AWOS                        106

LOCATION                     TUESDAY HEAT INDEX

LEOLA SDSU                          125

ABERDEEN ASOS                       121

MILBANK AWOS                        120

BIG STONE RAWS                      119

ORTONVILLE AWOS                     115

BOWDLE SDSU                         114

FAULKTON SDSU                       114

GRAND RIVER RAWS                    114

WHEATON AWOS                        114

SISSETON ASOS                       113

DAKOTA LAKES RESEARCH FARM SDSU     112

GETTYSBURG AWOS                     112

MCINTOSH SDSU                       112

MILLER AWOS                         112

FORT PIERRE RAWS                    111

MOBRIDGE ASOS                       111

GETTYSBURG SDSU                     110

LAKE COCHRANE RAWS                  110

PIERRE ASOS                         110

TIMBER LAKE SDSU                    110

HURON RAWS                          109

HIGHMORE SDSU                       108

BEAR CREEK RAWS                     107

MARSHALL COUNTY RAWS                107

SOUTH SHORE SDSU                    107

WATERTOWN ASOS                      107

EAGLE BUTTE SDSU                    106