The eastern third of the US could see extreme heat this week, as warnings predict temperatures rising above 100 degrees. The National Weather Service is warning at least 18 states that extreme heat, even record-setting and “dangerous” temperatures, is coming through Monday, June 29, 2026. According to the NWS, the extreme heat wave should last through the July 4 weekend.
The National Weather Service warned that the heat index — which measures how hot it feels to the body — could soar as high as 115 degrees. “A high or moderate extreme heat risk covers much of the US east of the Rockies on July 4-5, while a widespread slight risk will extend west to the Great Basin by July 7.” NWS forecast. Temperatures could also reach 80 degrees at night, which will provide some relief over the July 4 weekend, the NWS reports. The “significant” heat wave begins on Sunday, June 28, 2026.
“Dangerous heat will rise to record levels across the eastern two-thirds of the country this week,” the National Weather Service wrote on Twitter.sharing a map This shows that in at least 18 states, the purple color indicates that extreme heat is possible.
The National Weather Service warns that local ‘heat indexes’ could reach 115 degrees
Dangerous heat will extend to record levels across the eastern two-thirds of the country this week. Be sure to follow your local forecast information https://t.co/VyWINDk3xP And https://t.co/hWJVNNW095 pic.twitter.com/3xDWQINtpG
– National Weather Service (@NWS) 28 June 2026
NWS also warned That “a dangerous heat wave will hit the central and eastern US with the sun and continue through the July 4 weekend. Highs will be between 90-100 and heat indexes will be 100-110° (locally 115°). Warm nights will provide little relief. Stay hydrated, limit outdoor activity and seek A/C.”
According to the NWS, to better measure how people are perceiving higher temperatures, a heat index combines ambient air temperature with relative humidity.
“Dangerous record-breaking heat will increase across the central portion of the country and slowly move eastward. Wildfire conditions will remain severe across parts of the Southwest and Great Basin through Monday,” the NWS said. “For the northern Plains and upper Midwest, severe thunderstorms with the potential for widespread hail.”
(Photo by Tim Boyle/Getty Images)
Out west, temperatures are expected to vary greatly. “With an upper level trough over the western US, temperatures will remain cooler than average through Monday with highs 20-35 degrees below normal,” the NWS wrote.
“Across the eastern United States, a dangerous heat wave is expected on Sunday, with highs in the 90s and 100s… Dangerous heat will begin to rise across much of the central and eastern US on Sunday, while the West will remain below normal.”
National Weather Service offers tips for staying safe during extreme heat wave
“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun and check in with relatives and neighbors,” the National Weather Service suggests.
The National Weather Service also offered some tips for staying safe in extreme heat. they include:
- Stay hydrated at work sites. Take breaks in the shade when possible.
- Never leave children or pets unattended in hot cars. “Check before locking.”
- “Limit strenuous outdoor activities, find shade and stay hydrated.”
- “Check the elderly, the sick and those without AC.”
According to the NWS, “heat-related impacts” are expected for Wisconsin until at least Thursday, July 2, 2026.
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