Delaware is bracing for oppressive heat this Friday, July 25, with an extreme heat warning in effect for New Castle County, and a heat advisory issued for Kent and Sussex counties. The warnings are active from 10 a.m. to 9 p.m., as humid and dangerously hot air moves into the region.
According to the National Weather Service in Mount Holly, New Jersey, heat index values—which represent how hot it feels when humidity is factored in—will climb between 100 and 106°F (37.7 to 41.1°C) across Delaware, New Jersey, southeastern Pennsylvania, and northeastern Maryland.
In Delaware, here’s what Friday’s heat index could feel like:
Wilmington: 105°F (40.5°C)
Dover: 103°F (39.4°C)
Bethany Beach: 96°F (35.5°C)
Health risks increase sharply with these kinds of conditions. Exposure to this level of heat and humidity can lead to heat-related illnesses, especially among vulnerable populations like children, older adults, and those with chronic health issues.
Adding to the dangerous conditions, there’s a chance for severe thunderstorms to develop Friday afternoon and evening. While the entire state of Delaware could see storms, the most significant threat is expected north of Georgetown, particularly across New Jersey and eastern Pennsylvania.
The primary concern will be locally damaging wind gusts, though large hail and heavy rain bursts are also possible.
Looking ahead to the weekend, humid conditions will persist, although temperatures won’t be quite as extreme. Still, the risk of strong storms continues, especially on Saturday, July 27, when heavy downpours could trigger flash flooding in parts of the region.
The National Weather Service warns that although the heat wave may ease slightly over the weekend, the humidity will still be uncomfortably high, especially during the daytime hours.
What You Need to Know About Heat Alerts
A heat advisory is triggered when heat index values are expected to exceed 100°F (37.7°C) during the day, and nighttime temperatures stay above 75°F (23.8°C). An excessive heat warning, on the other hand, is issued when extreme heat is imminent or already occurring.
When the heat index climbs:
- Between 80–90°F (26.6–32.2°C): prolonged activity can lead to fatigue.
- Between 90–103°F (32.2–39.4°C): there’s a real risk of heat exhaustion, cramps, and even heat stroke.
- Between 103–124°F (39.4–51.1°C): dangerous conditions where heat stroke is possible.
- Above 125°F (51.6°C): extreme danger, with heat stroke highly likely.
These conditions limit the body’s ability to cool itself. High humidity levels reduce the rate of evaporation from sweating, making it harder to regulate body temperature.
Stay alert as Friday’s heat builds and afternoon storms become more likely, particularly in northern Delaware and nearby states.
