National Weather Service Weather Forecast Office

July 2011 was a very warm and humid month across the region.  An extreme period of heat and humidity occurred from July 16-20 when high temperatures were in the mid to upper 90s and lows were in the mid to upper 70s.  While July typically has periods of very warm and humid conditions, the very warm low temperatures were unusual.  Huron had 10 days where the low tempreature was at least 70 degrees.  The warmest low temperature of the month was 80 degrees on July 17.  This was the most number of days with a low temperature of at least 70 degrees since 1955.  Sioux City had 18 days with a low temperature of at least 70 degrees.  This was the most number of days with a low temperatures of 70 degrees since 1936.  The warmest low temperature was 79 degrees on July 20.  Finally, Sioux Falls had 11 days with a low temperature of 70 degrees or warmer.  The warmest low temperature was 80 degrees on July 17.  This was the most number of days at or above 70 degrees since 1974.   As a result of so many days above 70, all three cities saw an average low temperature for July that was near record.  Huron had the 2nd warmest average low temperature recorded at 68.1, Sioux City had the 3rd warmest average low temperatures recorded at 70.5 degrees, and Sioux Falls tied for the 3rd warmest average low temperature with 67.7 degrees.

While low temperatures were very warm for the month, the high temperatures did not approach any records.  All three cities were at least 10 degrees cooler than 1936 which is the warmest July on record.  None of the cities had an average high temperature in July that was in the Top 10.  Only Sioux City was close with an average high of 90.1 degrees which is the 13th warmest July on record.

Below are tables showing the average low, average high and average temperature for July 2011 for Huron, Sioux City, and Sioux Falls.  Also included are the records all of which occurred in 1936.