The Weather Prediction Center (WPC) has placed all of Iowa in its Day 3 through Day 7 Hazards Outlook for hazardous heat, signaling growing confidence that a significant heat wave could impact the state beginning late this weekend and continuing into next week.
This outlook means there is at least a 40% probability that widespread National Weather Service (NWS) Heat Advisory criteria will be met or exceeded somewhere within the highlighted area. While it does not guarantee that every community will experience hazardous heat, it does indicate that forecasters see a strong signal for dangerous heat conditions developing across a large portion of Iowa.
What Is Heat Advisory Criteria?
In Iowa, Heat Advisories are typically issued when heat index values are expected to reach 100°F or higher for several hours.
The heat index measures how hot it feels when air temperature and humidity are combined. During the summer, high humidity can make conditions feel significantly hotter than the actual temperature, increasing the risk of heat-related illnesses.
Heat index values above 100°F can create dangerous conditions, especially for those spending extended periods outdoors, individuals without access to air conditioning, older adults, young children, and those with underlying health conditions.
Forecast Models Continue to Show a Hot Pattern
Both the ECMWF (Euro) and GFS forecast models continue to show a period of above-normal temperatures across Iowa from Sunday through at least Tuesday.
On Sunday, June 28, the European model projects afternoon highs ranging from the mid-80s across eastern Iowa to the mid-90s across central and western Iowa. The GFS is slightly cooler, showing upper 80s across much of the state and low 90s across western Iowa.
By Monday, June 29, the heat intensifies. The European model forecasts temperatures near 90°F in eastern Iowa with mid to upper 90s across central and western Iowa. The GFS remains somewhat cooler in eastern Iowa with upper 80s but still shows low to mid-90s across central and western portions of the state.
The GFS continues the heat into Tuesday, June 30, with widespread low to mid-90s expected across nearly all of Iowa.
While there are some differences in the exact temperatures, both models agree on the overall pattern: a prolonged stretch of hot and humid conditions is likely.
Heat Index Values Could Exceed 100 Degrees
Perhaps more concerning than the actual temperatures is the expected humidity.
Both the Euro and GFS forecast heat index values between 100°F and 107°F during the Sunday through Tuesday time period. If these forecasts verify, many areas could meet or exceed Heat Advisory criteria for multiple consecutive days.
Several days of dangerous heat can be especially impactful because overnight temperatures often remain warm, limiting the body’s ability to recover from daytime heat stress.
Potential Impacts
If current forecast trends continue, residents across Iowa could face an increased risk of:
- Heat exhaustion
- Heat stroke
- Dehydration
- Increased stress on those with heart and respiratory conditions
Outdoor workers, athletes, those attending summer events, and anyone spending extended periods outside should closely monitor the forecast as details become clearer.
Stay Weather Aware
While the exact temperatures may change over the coming days, confidence is increasing that Iowa will experience a period of dangerous heat beginning late this weekend and continuing into next week.
The ISCN Weather Team will continue monitoring forecast trends and provide updates as confidence increases. Now is a good time to prepare by staying hydrated, limiting outdoor activities during the hottest part of the day, and ensuring family members, neighbors, and pets have access to cool environments.
Be sure to check back for updates and keep the ISCN Weather app installed for the latest forecasts, alerts, and weather information.