A prolonged stretch of hot, humid, and potentially dangerous weather is expected to begin across Iowa on Sunday and continue through at least Tuesday, with signs that the heat may linger through much of next week and possibly into the Fourth of July weekend.
The National Weather Service has issued an Extreme Heat Watch for much of Iowa from Sunday afternoon through Tuesday evening. Heat Advisories are also in effect for portions of western and northwest Iowa, where heat index values are expected to climb as high as 105 degrees. In southwest Iowa, heat index values may approach 108 degrees at times.
First True Summer Heat Arrives Sunday
Before the heat fully builds in, Saturday will remain relatively mild by late June standards, with many areas seeing highs in the upper 70s to lower 80s. Some clouds may linger through part of the day, especially across central and eastern Iowa.
By Sunday, a much hotter and more humid air mass will surge north into the state. Afternoon temperatures are expected to climb into the upper 80s and 90s, while dew points rise into the 70s. That combination will push heat index values above 100 degrees in many locations by Sunday afternoon.
Heat Index Values Over 100 Degrees
The most dangerous heat is expected Monday and Tuesday, when much of Iowa could experience heat index values between 100 and 108 degrees. Even if actual air temperatures remain in the low to mid-90s, high humidity will make it feel significantly hotter.
Overnight temperatures will also remain very warm, with lows only dropping into the mid to upper 70s in many areas. This is especially concerning because homes without air conditioning may not cool down much overnight, allowing heat stress to build over several days.
Heat Headlines Could Be Upgraded
The current Extreme Heat Watch may be upgraded to an Extreme Heat Warning for parts of Iowa if forecast confidence continues to increase. Some Heat Advisories may also be extended farther into next week.
The duration of this heat wave is one of the bigger concerns. While any single afternoon of heat can be dangerous, several consecutive days of high heat and humidity can significantly increase the risk of heat-related illness.
Storm Chances Before and During the Heat
There will be a chance for scattered showers and isolated thunderstorms Saturday night into Sunday morning. A few storms could be strong, especially across western and northern Iowa, with hail and gusty winds possible. However, the overall severe weather threat appears low for much of the state.
Additional thunderstorm chances may develop at times next week, especially during the evening and overnight hours. This type of pattern is often referred to as a “ring of fire,” where storm clusters ride around the edge of a large heat dome. These storms could briefly interrupt the heat in some areas, but they may also bring a risk for strong winds or heavy rain depending on their track.
Heat Safety
This is the type of heat that can become dangerous quickly, especially for outdoor workers, athletes, young children, the elderly, and anyone without reliable access to air conditioning.
Drink plenty of water, take frequent breaks in shaded or air-conditioned areas, and limit strenuous outdoor activity during the hottest part of the day. Check on relatives, neighbors, and anyone who may be more vulnerable to the heat.
Never leave children or pets inside a parked vehicle, even for a short time. Temperatures inside a vehicle can become life-threatening within minutes.
Looking Ahead
The heat is expected to continue beyond Tuesday in some form, with several forecast models suggesting hot and humid conditions may persist through much of next week. There are also signs that the pattern could last into the Fourth of July weekend, though details will depend on thunderstorm activity and any brief breaks in the heat.
Stay with IowaWeather.com for the latest forecast updates as heat headlines may be upgraded, extended, or expanded over the coming days.