North Iowa Faces Severe Storm Risk Overnight, Heat Index Could Top 100 Monday

NORTH IOWA — Forecasters are tracking a two-part weather threat for North Iowa that begins with overnight thunderstorms and ends with a chance of severe storms and dangerous heat Monday, according to the National Weather Service office in Des Moines.

The Weather Service placed the region under a marginal risk, or level 1 of 5, for severe storms from midnight to 6 a.m. Monday, with damaging wind cited as the main hazard. Thunderstorms were expected to move into northwest Iowa overnight and weaken as they track southeast at about 20 mph across northern Iowa through the early morning hours, the agency said in a 4:05 a.m. Sunday forecast packet.

Conditions are then expected to turn hot Monday afternoon, with heat indices forecast to reach 103 degrees in Mason City. Other communities in the outlook range from a heat index of 100 in Estherville to 107 in Fort Dodge and Ames, according to the Weather Service. The agency cautioned that morning storms and smoke aloft could still influence how hot temperatures actually get.

The Weather Service urged residents to take breaks in air conditioning or shade, drink plenty of water, and never leave children or pets unattended in vehicles, warning that heat illness is possible.

A more serious threat is expected Monday evening, when the Weather Service placed Mason City and much of North Iowa under an enhanced risk, or level 3 of 5, for severe storms. Storms are forecast to strengthen in the late afternoon and move southeast across Iowa through the evening at about 35 mph, the agency said.

Damaging wind and large hail are the primary threats for Monday evening, with forecasters saying gusts of 70 mph or higher are possible. Most hail is expected to measure an inch or less, though the Weather Service said an isolated storm could produce hail up to 2 inches in diameter. A tornado is also possible, mainly in northeast Iowa, along with heavy rain, according to the forecast.

The Weather Service said the evening severe weather threat will depend on how Monday morning’s storms evolve.