Northern Iowa Faces Severe Storm Threat, 100-Degree Heat Index Monday

MASON CITY, Iowa — North Iowa faces a dangerous combination of severe thunderstorms and extreme heat Monday, with forecasters warning of damaging winds, large hail and a possible tornado as temperatures push heat indices past 105 degrees.

The National Weather Service in Des Moines placed Mason City and the surrounding area under an enhanced risk, a level 3 out of 5, for severe storms late this afternoon into the evening. Damaging wind is the primary threat, forecasters said, with gusts of 70 mph or higher possible. Large hail up to 2 inches in diameter, roughly the size of a hen’s egg, and heavy rain are also possible, according to the National Weather Service.

A tornado is possible as well, mainly across northeast Iowa, forecasters said. Whether storms intensify later Monday night depends on how thunderstorms develop earlier in the day, according to the weather service.

The severe weather threat arrives alongside a Heat Advisory in effect from noon to 8 p.m. Monday. Highs in Mason City are expected to reach the upper 90s, with a maximum heat index of 100 degrees around midday, according to National Weather Service forecast data. Temperatures are forecast to cool into the mid-70s overnight before climbing again Tuesday.

The weather service urged residents to take precautions against heat illness, including taking breaks in air conditioning or shade, drinking plenty of water, and never leaving children or pets unattended in vehicles.

An Iowa Department of Natural Resources air quality alert also remains in effect for the eastern half of Iowa through Monday morning. People with heart or respiratory conditions should limit prolonged or heavy outdoor exertion, according to the DNR. Exposure to air pollutants such as particulate matter and ground-level ozone can cause headaches, difficulty breathing, irritated eyes and sinuses, chest pain, asthma attacks, fatigue, and irritated throat or increased coughing. Seniors, children and those with compromised immune systems face heightened risk, the weather service said.

Additional smoke is expected to move into the region behind a cold front Tuesday, which could bring renewed air quality concerns, according to the National Weather Service.