A National Weather Service heat advisory covers Denville and the rest of Morris County on Wednesday, July 15, 2026, from 10 a.m. to 8 p.m., with the heat index expected to climb as high as 103 degrees.
The advisory, issued by the National Weather Service office in Mount Holly, also takes in Sussex, Warren, and Hunterdon counties. Forecasters warn that the mix of high temperatures and humidity can trigger heat illness, and they urge residents to drink plenty of fluids, stay in air conditioning, keep out of the sun, and check on older neighbors and relatives.
Denville residents who do not have reliable air conditioning have two designated cooling centers open through the county Office of Emergency Management. The Denville Library at 121 Diamond Spring Road is open Monday through Friday from 8:30 a.m. to 6 p.m. and can be reached at 973-627-6555. The Denville Town Hall Community Room at 1 St. Mary’s Place is open weekdays from 8 a.m. to 4 p.m., with nights and weekends available as needed, at 201-919-1501.
A full list of cooling centers across all 39 Morris County towns is posted on the county Office of Emergency Management website. Residents can also dial 2-1-1 at any hour to find the nearest open site. It is the second stretch of dangerous heat to hit the area this month, after an extreme heat warning reshaped the Denville Days schedule over the July 4 weekend.
Officials say strenuous outdoor activity should be limited to early morning or evening, with frequent breaks in the shade. Heat stroke is a medical emergency. Anyone showing signs of heat exhaustion or heat stroke should be moved somewhere cool, and 911 should be called right away.
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