Uncharted Heat Index values

hot2.650.jpgAustin Schoen (left), Mark Schauer (center) and Tanner Schauer cool off on the Bumper Boats ride at Lilli Putt in Coon Rapids, Minn., on July 18, 2011. (MPR Photo/Nikki Tundel)

While we are calling this sweltering, oppressive atmosphere a Heat Wave, it equally worthy of being called a High Dew Point Warning. Yesterday afternoon and evening dew points, a very good indicator of the moisture in the atmosphere, were in the lower 80s over a large swath of southern Minnesota. It is very rare to observe sustained high dew points over a broad area this far north.

Dew point measurement can me impacted by the microclimate of the sensors location. We see dew points at their highest in southern Minnesota from mid July through about mid August. A number of us in the weather business believe that these seasonally high dew points are the results of the evapo-transpiration of the maturing corn corps across Iowa and southern Minnesota. Moisture is released back into the low levels of the atmosphere and we feel its affects.

A slight drop in dew points is seen for today. We may well see a few degrees of additional heat on the thermometer. That translates to Heat Index values of 105 to 115, in the shade, during the middle of the day. This is excessively sweltering when you add into the equation direct sunlight. Stay out of the sun today if you can. Unless you are standing in the lake.

Dogs and cats instinctly slow down in this weather. If your dog needs to have a walk, make it a quick trip early in the morning or in the evening. Provide plenty of water for pet during this sultry period.

Follow the advice from health officials with regard to your well being. Apply the number one rule; slow down. Dress in light colors with a brimmed hat.

Heat spell breaks a bit towards the end of the week. Just so you know; the climate records document the next seven to ten days as the warmest period during the calendar year.


The sensible temperature is about fifteen degrees warmer in the direct sunshine.


Think cool thoughts today.