Image from Weather.com

A significant and long lasting heat wave effected the area this week from June 30th through independence day to July 6th. The cause of the long stretch of hot weather was a large ridge of hot high pressure which pushed a huge very dry and extreamlly hot temperatures across the entire central and eastern half of the country. Nearly every central and eastern U.S state had at least one city hit 100 degrees in this heat wave.

Hot red glowing sunset Rochester,MN July 2nd 2012

Locally this heat wave was a significant one and one for the record books at Rochester airport. This heat wave was the worst one in a number of years according to many as we sweltered in heat for a week. It was certainly the warmest and longest I’ve delt with. From June 30th through July 6th every day was above 90.F in all areas and a couple days were in the upper 90s to lower 100s, with heat index values every day in all areas well into the 100 degree range, as dew points straddled each day from the low 70s to nearly 80.F! 2 of our official stations, Red Wing and Winona went above 100.F 2 of the days, This is the first time in many years that a heat wave has brought more then 1 day of 100 degree temperatures. At my location all days were well into the 90s and 2 of the days ended up being at or above 100., July 4th the high was 100.F,  but the warmest high temperature was 102.F on July 6th. This is the warmest temperature that I’ve experienced personally, before that it was 100.F in my hometown in NW Wisconsin which occurred in June of last year. I felt all 102 degrees of it and takes a toll fast. There was no relief at night either the warmest low at my station was 80.F on July 4th and again July 6th. During the evening of July 5th before I went to bed at 11:30pm the temperature was still 86.F which was stunning to be becuase I have not seen heat last this long into the night before. Effects of the very high temperatures caused power companies across some areas to ask residents to keep power usage to a minimal during the height of the afternoon hours. You could also see the effects of very warm temps and lack of rain taking a toll in our landscaping most people have had to water plants every day just to keep them from wilting. Unwatered lawns have been completely parched espesscailly in sites with poor soil and lots of sun. Corn crops are started to wilt from lack of rain and very high temperatures.

Highs temps reported in the heat wave/highest heat index values.

The highest official temperature during this heat wave came from Winona and Red Wing which both reported extreme heat of 102.F with heat index values of 109 and 111! I found it rather interesting that northerly stations were the warmest throughout the area. My theory in why these areas are warmer is because there river valley cities in low warm valleys. In the Rochester Metro area Downtown heat island effected weather stations were between 99 to 102.F. My station was 102.F. This brings the yearly total days at 90 or above to 18 and the days at or above 100 to 2 days. Officially the highest temperature at our cities official weather station at Rochester International Airport was 96.F and no 100s occurred. The records that occurred at the airport were several daily low temperature records. The difference in temps between Downtown and the Airport has been an ongoing study for me but theory on why Downtown areas of Rochester are so much warmer then the airport is because of how the city also sits in a river Vally but it is also becuase of the high concentration of large buildings and concrete forming a heat island effect. I did call NWS officials at both at Chanhassen and La Crosse and they confirmed the same theory on why there is a difference.