Extreme Heat Warning in Effect Through Tuesday as Iowa Faces Dangerous Week of Heat and Storms

 MASON CITY, Iowa — A dangerous and prolonged heat wave is gripping north Iowa and much of the state this week, with an Extreme Heat Warning in effect through Tuesday evening and heat index values forecast to exceed 100°F each day through the July 4th holiday weekend.

The National Weather Service office in Des Moines issued the warning early Monday morning, warning residents that temperatures in the 90s combined with high humidity will create life-threatening heat conditions for multiple consecutive days.

Heat Index Values Could Reach 109°F

According to NWS forecast graphics, heat index values — what the air actually feels like on exposed skin — are expected to be especially brutal Monday and Tuesday. In Des Moines, the heat index could reach as high as 109°F on Monday afternoon. Mason City is forecast to see heat indices of 106°F Monday, with values hovering between 93–101°F through Thursday.

There will be little overnight relief. Temperatures are expected to remain in the upper 70s and 80s overnight, meaning the human body will have limited opportunity to recover from the daytime heat stress before the next day’s heat builds again.

Severe Storm Risk Tonight in Northwest Iowa

On top of the heat, north and northwest Iowa face a separate weather threat tonight. The NWS has issued a Slight Risk (Level 2 of 5) for severe thunderstorms, primarily in northwestern Iowa, with the window for storm development running from approximately 9 p.m. Monday through 6 a.m. Tuesday.

The primary threats from any storms that develop include damaging winds of 60–70 mph and hail up to 1.5 inches in diameter — roughly the size of a quarter to a ping pong ball. A tornado or two cannot be ruled out, though tornado development is considered possible but not likely. Significant wind above 80 mph and hail larger than 2 inches are both considered unlikely.

Residents in storm-prone areas should stay weather-aware tonight, have multiple ways to receive warnings, and identify indoor shelter options in advance.

How to Stay Safe During Extreme Heat

With the heat wave stretching through at least the Fourth of July weekend, officials are urging Iowans to take the following precautions:

• Drink plenty of water throughout the day, even if you don’t feel thirsty
• Spend time in air conditioning, especially during the hottest part of the afternoon
• Take frequent breaks in shade or A/C if working or spending time outdoors
• Never leave children or pets unattended in a vehicle — temperatures inside a parked car can become deadly within minutes
• Bring pets indoors or ensure they have shade and access to plenty of water
• Avoid alcohol and caffeine, which contribute to dehydration
• Wear lightweight, light-colored, and loose-fitting clothing
• Check on elderly or ill neighbors and family members who may struggle in the heat
• Watch for signs of heat illness, including heavy sweating, dizziness, nausea, or confusion

When to Get Help

Heat exhaustion and heat stroke are medical emergencies. If someone stops sweating during extreme heat, has hot or red skin, confusion, or loses consciousness, call 911 immediately.