Iowa Under Extreme Heat Warning as Heat Index Nears 113; Severe Storms Possible Overnight

MASON CITY, Iowa — Dangerous heat will grip north Iowa through Monday, with heat index values in Mason City expected to reach 113 degrees this afternoon, according to the National Weather Service office in Des Moines.

An Extreme Heat Warning is in effect today for most of Iowa, including Mason City, Waterloo, Fort Dodge and Algona, the weather service said in a 5:47 a.m. briefing Sunday. An Extreme Heat Watch remains in effect for most of the state Monday, when temperatures are expected to feel similarly oppressive.

Forecast heat index values for Mason City show a climb from 77 degrees at 6 a.m. Sunday to a peak of 113 degrees at 3 p.m., before easing slightly to 95 degrees by 9 p.m., according to weather service data. Monday’s heat index in Mason City is forecast to peak at 102 degrees in the afternoon.

Relief is on the way by Tuesday, when heat index values in Mason City are expected to drop into the low 90s.

In addition to the heat, forecasters said severe thunderstorms are possible tonight into early Monday, with damaging wind gusts as the primary concern. The Storm Prediction Center has placed the Mason City area in a slight risk, or level 2 of 5, for severe weather, with the most likely window for storms between 9 p.m. and 6 a.m. Hail and heavy rain are listed as secondary threats, and storms are expected to move to the southeast at around 35 mph, the weather service said.

The severe weather threat represents an update from earlier forecasts, according to the weather service, which had raised the risk level for parts of Iowa overnight. Forecasters cautioned that the potential and timing for storms remain uncertain, though conditions Sunday night are expected to be favorable for severe weather to develop.

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

Health officials warn that heat exhaustion, marked by dizziness, thirst, heavy sweating, nausea and weakness, can progress to heat stroke if untreated. Heat stroke symptoms include confusion, dizziness and loss of consciousness, and can cause death or permanent disability without emergency treatment. Anyone showing signs of heat stroke should call 911 immediately, move the person to a cooler area, loosen their clothing and cool them with water or ice, according to guidance from the National Weather Service, the Centers for Disease Control and Prevention, and the National Institute for Occupational Safety and Health.