WASHINGTON — A dangerous heat wave driven by a strengthening heat dome is intensifying across much of the central and eastern United States, forecasters said on Tuesday, with record-high temperatures and oppressive humidity expected to grip large swaths of the country through the July 4 holiday weekend.
The National Weather Service warned that the “potentially historic” conditions will affect more than 200 million people, with daytime highs in the 90s and low 100s Fahrenheit (32-38 Celsius) and heat indices — the “feels like” temperature accounting for humidity — reaching 105-115 F (41-46 C) in many areas.
Extreme heat alerts cover portions of more than 30 states, with the highest risks across the Midwest, Ohio and Mississippi River valleys, mid-Atlantic and parts of the Southeast. Overnight lows are forecast to offer little relief, remaining in the 70s in many places.
Forecasters said the heat will expand eastward and persist, with numerous daily records possible and some areas challenging all-time highs. Cities including Chicago, Minneapolis, Nashville, Atlanta, Washington and New York could see consecutive days of extreme conditions.
The National Weather Service has placed tens of millions under extreme heat watches, warnings or advisories, noting that heat is the leading weather-related cause of death in the U.S.
No widespread casualty figures were immediately available, but officials urged precautions amid the holiday travel and outdoor celebrations. Emergency services and public health authorities in affected regions have activated heat response plans.
The heat dome is expected to remain in place for several days, with the peak intensity aligning with Independence Day festivities.
The story is developing.
