Mid-Summer Heat Wave Expected This Week

Record Breaking Temperatures Possible

After a cooler start to the month of July, we are finally in for some summer heat. The average temperature for the first 17 days of July in Sioux Falls has been 1.6 degrees cooler than normal, and in Pierre that number is even larger at 1.9 degrees cooler than normal. That all changes as we head into the middle of the week.

An excessive heat watch has already been issued for dangerous heat index values and is highlighting all of the Sioux Empire for Tuesday through Friday. Anyone include in red in the image below is under that watch which starts for places in central South Dakota as early as Tuesday, but for most that are east of the James River, that will not go into effect until Wednesday morning.

Excessive Heat Watch: a prolonged period of hot temperatures is expected. The combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses are possible.

While temperatures will be extreme the next severe days, the hottest stretch of weather looks to be between Wednesday and Thursday. Our “feels like temperature,” also known as the heat index, over that stretch will be between 100 and 110 degrees! The heat index is calculated by take into effect the temperature as well as the humidity, using either dew point or relative humidity. Exposure to full sunshine can increase heat index values by up to 15°F.


Over the last 30-years, heat has killed more people on average than any other weather phenomenon, so remember these heat safety tips. Make sure you are staying hydrated throughout the week as dehydration can lead to heat exhaustion. Wear light colored clothing if you plan on being outdoors for an extended period of time and make sure to take frequent breaks if working outdoors. NEVER leave a child or pet alone inside a car as it can lead to death in a matter of minutes.

While some areas saw a few hot days earlier this summer, it has actually been a while since we saw this kind of widespread heat. Some places have a shot at breaking high temperature records over the next three to four days, while others might hit the century mark for the first time in years! For example, if we make it through Thursday, it would mark 14 straight years since Brookings had recorded a 100 degree temperature.

Your best bet? Stay indoors in an air conditioned building or go find a pool or pond/lake to jump and stay safe! There is a break from the heat on the way by the weekend.

Brandon Spinner
Chief Meteorologist
Twitter: @wxspinner89
Facebook: Meteorologist Brandon Spinner

Categories: Weather Blog, Weather Blog-imported, Weather-imported