National Weather Service Weather Forecast Office

The heat wave has broken across the Northern Plains, as cooler and much drier air has pushed south behind a cold front. Following are some statistics of interest about the temperatures and moisture during this stretch of excessive heat and humidity.

Several records for Record High Minimum Temperatures have been either tied or broken during this heat wave:

• This heat wave produced 2 of the 5 warmest low temperatures ever recorded in Huron.  The low temperature of 81 degrees in Huron on July 19 was the 2nd warmest low temperature in history (tied with July 20, 1934 & July 15, 1931).  Additionally, the low temperature of 80 degrees on July 17 is now the 5th warmest in history (tied with July 9, 1936). The warmest low temperature ever recorded in Huron is 82 degrees, which occurred July 11, 1936.
• The low temperature of 80 degrees in Sioux Falls on July 17, was the third warmest low in history (tied with August 16, 1988 & July 11, 1966). The warmest low temperature ever recorded is 81 degrees, which occurred on August 14th, 1938 & July 12th, 1936.  Note, the low temperature of 79 degrees on July 19 fell just shy of the Top 5, tying with numerous other dates for 6th place.

While the low temperatures were tying and breaking records, the hot daytime high temperatures did not, neither for individual daily records nor for duration of time. The 6 days with high temperatures at or above 90 degrees did not even place in the 50 longest stretches of 90+ degree heat at our 4 long-term climate locations (Sioux Falls, Sioux City, Huron, Mitchell).

This heat wave may instead be remembered more for the humidity than the persistance of extremely warm daytime temperatures. Several days of dew points in the mid 70s to around 80 degrees, combined with the air temperatures in the 90s to just above 100 degrees, produced multiple days with triple digit heat indices. Below is a table of the highest heat index recorded at various locations since late Sunday afternoon.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
613 PM CDT WED JUL 20 2011

...MAXIMUM HEAT INDEX OBSERVED SINCE LATE SUNDAY AFTERNOON...

OBSERVATIONS ARE COLLECTED FROM A VARIETY OF SOURCES WITH VARYING 
EQUIPMENT AND EXPOSURES. NOT ALL DATA LISTED IS CONSIDERED OFFICIAL. 
THE NATIONAL WEATHER SERVICE THANKS ITS PRIVATE AND PUBLIC PARTNERS 
FOR PROVIDING US WITH THIS DATA.

...IOWA...

...BUENA VISTA COUNTY...

3 WSW LAKESIDE (1489 FT)(OTHER-MTR)             535 PM JUL 18      109 F
2 ENE TRUESDALE (1329 FT)(IADOT)                348 PM JUL 18      121 F

...CHEROKEE COUNTY...

1 S CHEROKEE (1227 FT)(OTHER-MTR)               435 PM JUL 18      119 F
2 ENE CHEROKEE (1312 FT)(APRSWXNET)             518 PM JUL 18      124 F

...CLAY COUNTY...

3 W DICKENS (1484 FT)(IADOT)                    703 PM JUL 18      115 F
3 WNW SPENCER (1338 FT)(ASOS)                   653 PM JUL 18      118 F

...DICKINSON COUNTY...

1 E WAHPETON (1397 FT)(AWS)                     714 PM JUL 18      111 F
4 NW WAHPETON (1527 FT)(APRSWXNET)              715 PM JUL 18      115 F

...IDA COUNTY...

1 NW IDA GROVE (1233 FT)(IADOT)                 620 PM JUL 18      111 F

...LYON COUNTY...

ROCK RAPIDS (1345 FT)(IEM)                      717 PM JUL 18      123 F
1 NNE INWOOD (1473 FT)(IEM)                     521 PM JUL 17      124 F

...O''BRIEN COUNTY...

3 NNE SHELDON (1420 FT)(OTHER-MTR)              535 PM JUL 18      114 F

...OSCEOLA COUNTY...

SIBLEY (IEM)                                    751 PM JUL 18      119 F

...PLYMOUTH COUNTY...

2 WSW LE MARS (1197 FT)(OTHER-MTR)              515 PM JUL 18      119 F

...SIOUX COUNTY...

1 WSW ORANGE CITY (1411 FT)(IADOT)              510 PM JUL 17      118 F
1 NE SIOUX CENTER (1463 FT)(APRSWXNET)          518 PM JUL 17      124 F
2 SSW ORANGE CITY (1414 FT)(OTHER-MTR)          535 PM JUL 18      124 F
1 N SIOUX CENTER (1480 FT)(AWS)                 719 PM JUL 18      125 F

...WOODBURY COUNTY...

4 N SIOUX CITY (1246 FT)(APRSWXNET)             834 PM JUL 18      111 F
3 SSE CORRECTIONVILLE (1400 FT)(MESOWEST)       500 PM JUL 18      113 F
4 N SIOUX CITY (1246 FT)(AWX)                   410 PM JUL 18      113 F
1 W SERGEANT BLUFF (1102 FT)(ASOS)              652 PM JUL 18      117 F
1 SSE SIOUX CITY (1195 FT)(IADOT)               550 PM JUL 18      125 F

...MINNESOTA...

...COTTONWOOD COUNTY...

3 NNE WINDOM (1410 FT)(OTHER-MTR)               432 PM JUL 18      117 F

...JACKSON COUNTY...

2 NNE JACKSON (1446 FT)(OTHER-MTR)              633 PM JUL 18      111 F

...LINCOLN COUNTY...

3 S HENDRICKS (1808 FT)(MNDOT)                  449 PM JUL 18      120 F
3 W ARCO (1748 FT)(APRSWXNET)                   435 PM JUL 18      120 F

...LYON COUNTY...

1 NNE TRACY (1338 FT)(OTHER-MTR)                552 PM JUL 18      113 F
2 W MARSHALL (1177 FT)(OTHER-MTR)               515 PM JUL 18      117 F

...MURRAY COUNTY...

1 W SLAYTON (1624 FT)(OTHER-MTR)                455 PM JUL 18      110 F

...NOBLES COUNTY...

2 NE WORTHINGTON (1574 FT)(OTHER-MTR)           415 PM JUL 18      110 F
2 W WORTHINGTON (1584 FT)(IEM)                  741 PM JUL 18      125 F

...PIPESTONE COUNTY...

1 SSW PIPESTONE (1735 FT)(OTHER-MTR)            632 PM JUL 18      114 F

...ROCK COUNTY...

2 SSW LUVERNE (1430 FT)(OTHER-MTR)              454 PM JUL 18      110 F
LUVERNE (1455 FT)(IEM)                          633 PM JUL 18      122 F

...SOUTH DAKOTA...

...BEADLE COUNTY...

1 N HURON (1289 FT)(ASOS)                       755 PM JUL 18      113 F

...BROOKINGS COUNTY...

2 W BROOKINGS (1647 FT)(OTHER-MTR)              555 PM JUL 19      103 F
VOLGA (APRSWXNET)                               517 PM JUL 18      119 F
1 E BROOKINGS (1676 FT)(APRSWXNET)              510 PM JUL 17      120 F
ELKTON (1748 FT)(IEM)                           633 PM JUL 18      122 F

...BRULE COUNTY...

1 S CHAMBERLAIN (1738 FT)(ASOS)                 452 PM JUL 18      115 F
1 WSW CHAMBERLAIN (1466 FT)(IEM)                551 PM JUL 18      118 F

...CHARLES MIX COUNTY...

9 W PLATTE (1654 FT)(RAWS)                      535 PM JUL 18      100 F
3 W GEDDES (1710 FT)(RAWS)                      441 PM JUL 18      113 F
4 SE DANTE (1446 FT)(IEM)                       331 PM JUL 18      116 F
1 SSE WAGNER (1475 FT)(NONFEDAWOS)              355 PM JUL 18      121 F

...CLAY COUNTY...

VERMILLION (1130 FT)(IEM)                       631 PM JUL 18      119 F
1 SSW VERMILLION (1147 FT)(NONFEDAWOS)          555 PM JUL 18      122 F

...DAVISON COUNTY...

ETHAN (1300 FT)(AWS)                            720 PM JUL 18      112 F
3 N MITCHELL (1302 FT)(ASOS)                    753 PM JUL 18      115 F
1 S MITCHELL (1295 FT)(IEM)                     821 PM JUL 18      125 F

...GREGORY COUNTY...

1 ESE GREGORY (2168 FT)(NONFEDAWOS)             355 PM JUL 18      110 F

...HUTCHINSON COUNTY...

1 SE PARKSTON (1415 FT)(NONFEDAWOS)             515 PM JUL 18      122 F
PARKSTON (1400 FT)(IEM)                         521 PM JUL 17      124 F

...JERAULD COUNTY...

2 ESE WESSINGTON SPRINGS (NONFEDAWOS)           655 PM JUL 18      118 F

...LAKE COUNTY...

1 NE MADISON (1673 FT)(IEM)                     511 PM JUL 17      116 F
2 ENE MADISON (1715 FT)(OTHER-MTR)              750 PM JUL 18      118 F

...MINER COUNTY...

HOWARD (IEM)                                    733 PM JUL 18      112 F

...MINNEHAHA COUNTY...

GARRETSON (IEM)                                 516 PM JUL 17      110 F
2 N SIOUX FALLS (1427 FT)(ASOS)                 756 PM JUL 18      111 F
5 W SIOUX FALLS (1505 FT)(APRSWXNET)            719 PM JUL 18      116 F
BRANDON (IEM)                                   506 PM JUL 17      119 F

...MOODY COUNTY...

FLANDREAU (1568 FT)(IEM)                        521 PM JUL 17      123 F

...TURNER COUNTY...

4 SSW MARION (1479 FT)(IEM)                     711 PM JUL 18      112 F

...YANKTON COUNTY...

2 NNE YANKTON (1305 FT)(OTHER-MTR)              515 PM JUL 18      118 F
YANKTON (IEM)                                   607 PM JUL 18      119 F

$$