US enters first major heat wave of 2025

The extreme heat is expected to intensify as it shifts to the East Coast early next week, with temperatures reaching the highest level on the NWS's HeatRisk tool: Level 4, or "Extreme."

"Numerous daily record highs and warm lows are likely," the NWS said. "Light winds, sunny days, and a lack of overnight cooling will significantly increase the danger."

The capital city Washington could see highs of 99 degrees Fahrenheit (37 degrees Celsius) on Monday and 101F on Tuesday.

This level of heat can be dangerous for anyone without access to effective cooling and hydration, especially those engaged in prolonged outdoor activity, the NWS warns.

Designated cooling centers -- including recreation centers and libraries -- will be open during business hours, the mayor's office announced. Homeless residents will have access to shelters.

Overnight lows may remain around 80F in urban areas such as Washington, Baltimore, Philadelphia, and New York City.

Fueled by human-caused climate change, 2024 was the warmest year on record globally -- and 2025 is projected to rank among the top three.