Heat wave and high humidity will blast much of the eastern US this week,
meteorologists say
[June 29, 2026]
By MARC LEVY
A long and dangerous heat wave will blast a large swath of the central
and eastern United States this week, the National Weather Service said,
with temperatures rising ahead of the July Fourth holiday and feeling
even hotter because of the high humidity that's arriving with it.
Already, parts of the U.S., especially Phoenix and central Texas, and
much of the Southwest were experiencing temperatures around 100 F (38 C)
on Sunday, while the weather service warned of severe wildfire
conditions developing across much of the West as new fires popped up
across the region.
On Sunday, well over 130 million Americans across southern and Great
Plains states were under moderate to severe heat risk conditions,
according to weather service maps, with that area forecast to expand and
temperatures to intensify as the week drags on.
Forecasters say several days of high temperatures — some above 100
degrees F — will settle in across the lower Great Lakes, the
mid-Atlantic and the Mississippi and Ohio River valleys. Some record
highs could be set in areas from the lower Great Lakes to the
mid-Atlantic and New England later in the week, said weather service
meteorologist Bryan Putnam.
A number of big cities could see their highest temperatures of the year
so far as they host World Cup matches and celebrations for America’s
250th anniversary.
Feeling the heat will be the East Coast cities of New York,
Philadelphia, Washington and Baltimore, and Midwestern and Great Lakes
cities including Chicago, Indianapolis, St. Louis and Detroit. Southern
cities including Dallas, Little Rock, Arkansas, and Memphis, Tennessee,
will also see high temperatures.
High heat will last into next weekend across the Great Plains, the
Southeast and the mid-Atlantic, the weather service said.
Temperatures will reach well into the 90s and low 100 degrees Fahrenheit
(mid to high 30s Celsius), the weather service said. High humidity will
lead to heat indexes of 100 to 110 degrees F (40 C to 43 C), and as high
as 115 F (46 C).
“That’s heat that’s impactful to anyone,” Putnam said. “It’s not just
older adults or younger children or people who are spending a ton of
time outdoors, maybe straining themselves a little more than normal.
This is heat that really could impact everyone, especially with people
outdoors going into the holiday weekend.”
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The heat index, which factors in humidity and is included on many
weather forecasts, provides a sense of how hot it really feels — and
what’s dangerous for prolonged exposure or strenuous activity.
AccuWeather meteorologist Tyler Roys said temperatures will be
significantly above normal. For instance, in Washington, highs
around July Fourth average around 89 degrees F (32 C), while
Indianapolis averages around 85 degrees F (29 C). But this week,
both cities will be hotter by 10 or 11 degrees F, Roys said.
The high pressure system — an area of dry, sinking air — creating
the heat will act like a “rock” that will force storms to go around
it and limit rainfall across the East, Roys said. That's sometimes
called a “heat dome.”
Nightly lows in the 70s F (21 to 26 C) or even high 80s won’t
provide much relief, meteorologists said.
For those who don't have air conditioning, especially in Eastern
Seaboard cities like New York where lows may not dip below 80 F (27
C), it’s going be miserable to sleep, Roys said.
Roys also said this is a primetime for heat-related illnesses
because people's bodies aren’t able to recover and cool off.
During extreme temperatures, limit outdoor activity, stay hydrated
and ensure access to air-conditioning and other cooling areas, the
weather service said.
The weather service said it expected extremely dry and windy
conditions that could promote rapid wildfire spread across the Great
Basin and the Southwest on Sunday.
In hot, windy conditions near the Colorado-Utah border, three
firefighters working for the U.S. Wildland Fire Service and U.S.
Forest Service were killed, and two others sustained burn injuries,
when they were overcome by flames from fast-moving wildfires.
Wildfire activity has intensified across the Western U.S. as hot,
dry and windy weather fueled flames in Utah, Colorado, Arizona and
elsewhere.
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