New sweltering heat wave to feature 100 F temperatures in East

A new round of heat combined with high humidity will build in the eastern United States from Sunday to Tuesday and some areas will challenge record highs set in the 1800s.

Temperatures will again surge to well above the historical average in much of the eastern United States from Sunday to Wednesday during what is typically the hottest time of the year for many locations, AccuWeather meteorologists warn. The heat will create opportunities to enjoy the pool or beach, but conditions can be dangerous.

The East will join in on what much of the West has been experiencing in terms of heat. Nationwide on Sunday, 245 million people will experience temperatures of 90 degrees Fahrenheit or higher, with at least 30 million to reach 100 or higher.

Heat and humidity often go hand in hand in the middle of July for the East, and conditions for the first part of the new week will be another example. However, considering that temperatures will surge to 5-15 degrees above the historical average, combined with high humidity, intense sunshine and light winds, it's going to feel searing.

"In some cases, such as in Charlotte and Raleigh, North Carolina, daily record highs dating back to the 1800s will be challenged on multiple days in the coming week as afternoon temperatures hover near the 100-degree mark," AccuWeather Senior Meteorologist Reneé Duff said.

In other locations, such as in Roanoke, Virginia, Baltimore and Washington, D.C., highs on a few days this coming week near 100 will rival territory experienced during the blistering summer of 1988.

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But even farther to the north, such as the zone from Philadelphia to Pittsburgh, New York City and Boston, highs in the 90s will signal a moderate heat wave as high temperatures of 90 degrees or higher for three or more days in a row are generally accepted as a heat wave in the Northeast. AccuWeather has taken steps to raise awareness of the intensity and duration of hot conditions through its HeatWave Counter and Severity Index™.

As high as actual temperatures get, the combination of heat, humidity, sun and light winds will make matters more extreme for several hours during the day.

Portions of the Southeast states will experience AccuWeather RealFeel® Temperatures of 105-110 F over multiple days, but even in portions of the Northeast, RealFeel® Temperatures will approach and even top 100.

As is often the case in large cities, the buildup of heat in paved and concrete areas can take many hours to cool down at night and may just reach the comfort zone as the sun rises the next day.

Experts urge people to avoid strenuous activity during the midday and afternoon hours and increase their intake of non-alcoholic fluids. When possible, seek air-conditioned environments or cooling stations. A brief cool shower can work wonders for those who do not have access to air conditioning. Preventative measures can help people avoid a trip to the hospital due to heat exhaustion or heat stroke.

Without a strong area of high pressure nearby to suppress columns of rising air that can form clouds, spotty, pop-up afternoon and evening thunderstorms can occur just about anywhere in the East.

However, because a zone in the Midwest will be quite active for thunderstorm complexes through the first part of the week, some of these long-lived severe storms can reach into the Northeast and central Appalachians with incidents of high winds and torrential downpours.

By the middle of the week, a dip in the jet stream will develop in the eastern half of the U.S. allowing a sweep of cooler and less humid air to sweep through the Northeast and into at least part of the Southeast states. At the very least, heavy, gusty and locally severe thunderstorms will mark the leading edge of the push of cooler air.

"There is the potential for the cool push to stall out near the Gulf and southern Atlantic coasts later [in the new] week," Duff said.

This sort of weather maneuver is not uncommon for July and could lead to a marked uptick in showers and thunderstorms for multiple days where the dry air from the northwest does not reach.

In the wake of the cool front, temperatures will be trimmed back considerably from 5-15 degrees above the historical average to 5 and perhaps 10 degrees below the historical average or a downward temperature trend of 25 degrees in some locations.

Pattern may bring return of smoky conditions

The orientation of the jet stream may bring down more than just cooler air from Canada later next week.

"There are a number of large wildfires burning in western and central Canada, and the smoke from these fires will sweep into much of the Midwest and perhaps even into parts of the eastern U.S. later next week," AccuWeather Meteorologist Brandon Buckingham said.

Whether that smoke is just harmless high-flying haze or low-level visibility with air quality issues will depend on atmospheric conditions.

Wildfires in Canada resulted in bouts of low visibility and poor air quality in portions of the Midwest and Northeast on multiple occasions in the spring and summer of 2023.

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