Extreme Heat Warning Issued for North Iowa: What You Need to Know This Week

MASON CITY, Iowa — The National Weather Service has issued an Extreme Heat Warning for much of Iowa, including the Mason City area, effective today through Tuesday, as a dangerous heat wave settles over the region with heat index values expected to top 100°F for multiple days.

Extreme Heat Warning in Effect Through Tuesday

The NWS office in Des Moines upgraded the previously issued Extreme Heat Watch to an Extreme Heat Warning for northeast Iowa early Sunday morning. Forecasters say temperatures in the 90s combined with high humidity will drive heat indices well above 100°F each afternoon this week — conditions that can quickly become life-threatening.

For Mason City specifically, the heat index forecast shows afternoon highs reaching 95°F Sunday, climbing to 98°F on Monday and Tuesday. Overnight temperatures will offer little relief, staying in the upper 70s and 80s through the week.

Heat Index Forecast for Mason City

The extreme heat is expected to persist through the entire week, including heading into the Fourth of July holiday weekend.

Severe Storm Threat Monday Evening

In addition to the dangerous heat, North Iowans should be aware of a separate weather threat Monday evening. The Storm Prediction Center has placed northwest Iowa under a Level 2 (Slight Risk) for severe thunderstorms on Monday, June 29, with the highest storm chances in the Spencer and Algona areas.

Storms are expected to develop after 7 PM and continue through the overnight hours. Primary threats include damaging winds and large hail, with tornadoes also possible. Residents are urged to stay weather-aware Monday evening, have multiple ways to receive warnings, and identify indoor shelter locations ahead of time.

How to Stay Safe in the Heat

The NWS urges all North Iowans to take the following precautions during the heat wave:

• Drink plenty of water, even if you don’t feel thirsty
• Never leave children or pets unattended in vehicles — car interiors can reach deadly temperatures within minutes
• Take frequent breaks in shade or air conditioning, especially during the hottest part of the day (typically 1–5 PM)
• Bring pets indoors or ensure they have shade and plenty of water
• Avoid alcohol and caffeine, which can accelerate dehydration
• Wear lightweight, light-colored, loose-fitting clothing when outdoors
• Check in on elderly or ill neighbors and family members who may be more vulnerable to heat illness

Recognizing Heat Illness

Watch for signs of heat exhaustion — heavy sweating, weakness, cold or clammy skin, nausea, or fainting. Heat stroke is a medical emergency: if someone has hot, dry skin and a high body temperature, call 911 immediately.