Storms moving through Iowa on Tuesday are ushering a big change in our weather. Extreme heat is forecast to settle in over the Central and Northern Plains, including the state of Iowa. A ridge will develop with the weather pattern, leading to high heat and humidity to build north from the southwest US. That ridge will stay in place for a number of days leading to persistent dangerous conditions.
The highest heat index reading in Des Moines since 1980 was 118º on July 26, 1997. We could come close to this on Thursday afternoon when heat index values are expected to reach 115º.
An Excessive Heat Watch begins at 11 a.m. on Wednesday morning and continues through 7 p.m. Friday. What this means is heat index values are expected to reach or exceed 110°F and not fall below 75°F for at least a 48 hour period, beginning in the next 12 to 48 hours. Plan to suspend all major daytime outdoor activities if a warning is issued. If you do not have air conditioning, locate the nearest cooling shelter or discuss staying with nearby family or friends who have air conditioning.
Heat is the No. 1 weather killer in the United States. There are a few ways you can minimize your risk of heat illness or even death. Minimize your time outside, especially during the hottest part of the day. Stay in the air conditioning. If being outside is necessary, wear light-colored and loose clothing. Drink lots of water even if you don’t feel thirsty. Avoid alcohol and caffeine. And watch out for children and the elderly. The young and very old are most at risk of health risks associated with heat exposure.
The heat index is what the temperature feels like to the human body. Added moisture in the air prevents our bodies from cooling off properly. Sweat is not able to evaporate from your body as efficiently, thus the body cannot cool off as it should. 90% of the body’s cooling happens because of the evaporation of sweat.
At a heat index of 90 to 105, sunstroke, heat cramps, or heat exhaustion POSSIBLE with prolonged exposure and/or physical activity.
At a heat index of 105 to 130, sunstroke, heat cramps, or heat exhaustion LIKELY, and heatstroke POSSIBLE with prolonged exposure and/or physical activity.