Dangerous heat wave to envelop 170 million Americans through late June

Record-smashing daytime temperatures near 100 degrees are expected for millions from the Plains to the East Coast this week, while nighttime temperatures may stay above 80 in some metropolitan areas.

A massive heat dome enveloping much of the central and eastern U.S. this week will lead to levels of heat and humidity not seen in June in many years, warn AccuWeather meteorologists.

High temperatures approaching and even exceeding 100 degrees are expected over more than three dozen states stretching from the Plains to New England through at least the middle of the week, challenging many long-standing records.

There will be little relief at night, with some urban areas failing to fall below 80 for multiple nights in a row, increasing the risk of heat-related ailments such as heat exhaustion or stroke.

Extreme heat builds east

The heat dome that will envelop the East has its origins in the Plains and Midwest, where readings in the 90s and even above 100 have been commonplace since late last week. The core of this extreme heat will build east this week, warn AccuWeather meteorologists.

"Dangerous heat will maximize across much of the Northeast and mid-Atlantic early this week," said AccuWeather Meteorologist Jacob Hinson. "Bright sun and humid conditions will cause AccuWeather RealFeel® Temperatures to peak above 100 degrees for millions."

In major cities such as Washington, D.C., Baltimore, Philadelphia and New York, the mercury is forecast to get very close to or even hit 100 for a few days, through at least Tuesday, which would mark the first time for some in many decades since triple-digit heat has been experienced in June.

Even parts of eastern and northern New England, including Boston and Portland, Maine, which are sometimes excluded from extreme heat domes, will come within a few degrees of 100 when the heat peaks on Tuesday.

At night, temperatures will struggle to fall below 80 in many urbanized areas, especially along the Interstate 95 corridor in the mid-Atlantic. To put in context how unusual this is for the month of June, in both Newark, New Jersey, and Philadelphia, there has never been a two-day stretch where low temperatures were 80 or higher, which AccuWeather is forecasting this week for three consecutive nights in both cities.

While the heat will not be as extreme farther west across wide swaths of the interior Northeast, Ohio Valley, Midwest and Tennessee Valley regions, the mercury will still reach well into the 90s under the dome through at least midweek. This includes large metropolitan areas such as Cincinnati, Detroit, Indianapolis, Memphis, Pittsburgh and St. Louis.

In Chicago and New York, the AccuWeather HeatWave Severity Index™, a scale that tracks the duration and severity of heat waves, indicates that the ongoing or forthcoming heat spell into this week will be worse than any experienced since the scale's inception in 2023.

As Hinson pointed out, humidity will also play a role in how hot it will feel this week. AccuWeather RealFeel® Temperatures of over 100 will become common outside of normally cooler mountainous areas into midweek, and they could be as high as 110-115 degrees in the mid-Atlantic away from the coast.

Cooling thunderstorms can offer brief reprieves from the heat, but not the humidity, in some areas this week. In addition to gusty storms on the periphery of the heat dome from the Plains to New England, pop-up thunderstorms can bubble up and fizzle out in a random nature, especially across the South.

A more significant intrusion of thunderstorm activity is expected to unfold along a battle zone on the heat dome's northeastern periphery from the Great Lakes to the Northeast and northern mid-Atlantic beginning Wednesday.

With more cloudiness and rain in the forecast then, temperatures will come down from their peaks on Monday and Tuesday, but still likely run well into the 90s for most in the mid-Atlantic.

Heat is the number one weather-related killer

Due to its cumulative effect on the human body, prolonged exposure to hot weather can kill.

According to Scientific American, extreme heat is the number-one weather-related cause of death in the U.S., and it kills more people most years than hurricanes, floods and tornadoes combined. The risk of death is especially elevated for those who lack air conditioning or work outdoors.

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"Vulnerable people, such as the elderly or young children, are most susceptible to heat-related illness," said Hinson. "Caution should be taken if spending any appreciable amount of time outside, such as by staying hydrated with non-alcoholic beverages, taking frequent breaks and seeking shade."

With the New York City mayoral primary election on Tuesday, those planning on voting in person and possibly waiting in lines outside in the heat should take precautions, such as bringing bottles of water and wearing light-colored, loose-fitting clothing. Ground temperatures in the normally-hotter, pavement-heavy parts of the City on Tuesday can easily top 100, while RealFeels® may reach 105.

Outdoor sporting events, from youth to professional leagues, will also be impacted by the extreme heat, even deep into the evening hours, as temperatures will be slow to fall after dark.

The safety of pets should also be considered during the heat wave. In many municipalities, such as the entire Commonwealth of Pennsylvania, it is illegal to tether dogs outside in the heat without access to cool water and shelter.

For those without consistent access to air-conditioned environments, hundreds of cooling centers are available across all states expected to be impacted by the extreme heat. The National Center for Healthy Housing maintains a webpage with contact information by state to find such cooling centers.

Additional tips to stay safe in and beat the heat can be found here.

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