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Sunday to mark peak of dangerous heat wave from Boston to Washington, DC

By Alex Sosnowski, AccuWeather senior meteorologist
July 21, 2019, 9:16:02 AM EDT


Millions of Americans remain under excessive heat warnings from the Eastern Seaboard to the central Plains, where AccuWeather RealFeel® Temperatures will once again dangerously soar past the century mark.

Power companies have braced for a surge in energy consumption due to the far-reaching heat wave, which will bring another day of temperatures soaring into the 90s and lower 100s from the southern Plains to the Ohio Valley and Northeast on Sunday.

Close to 60 million Americans live along the Interstate-95 corridor from New England to the mid-Atlantic, where daily record-high temperatures are once again in jeopardy to end the weekend.

Sun RF July 20


"With temperatures starting the day at near levels that are closer to the day's average high, Sunday could be the hottest day of this heat wave all along the Interstate-95 corridor from Boston to New York City, Philadelphia and Washington, D.C.," according to AccuWeather Senior Meteorologist Kristina Pydynowski.

The summer scorcher will bring highs in the 90s to near 100 F with AccuWeather RealFeel® Temperatures forecast to spike near 110 in some urban areas for several hours during the late morning and afternoon.

Temperatures around 100 F are expected in the cities of Washington, D.C., Baltimore, Philadelphia, New York City and Boston once again on Sunday.

Mon RF July 20


At this level, the hot July months of the past in 2012, 2011, 1991, 1980 and 1930 will be rivaled. Forecast temperatures are 10-15 degrees Fahrenheit above average, even for the middle of summer.

For a time, it may feel just as hot in Washington, D.C., as Death Valley, California. While the actual temperature may be higher in Death Valley, when compared to the nation's capital, humidity levels near the Chesapeake Bay will be substantially higher than that of the deserts.

For example, dew point temperatures will range from the teens to the lower 30s in the deserts, but will be in the 70s to the lower 80s near the Chesapeake Bay. The dew point is the temperature that the air becomes saturated with water vapor when the air is cooled. When this happens, the relative humidity reaches 100 percent.

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However, near 100-degree temperatures with high humidity is significantly different than that of the typically low humidity locations of the Southwest.

Both areas are dangerous in the heat, but with the combination of vast-paved areas and heavy population, the health risk is significantly higher for more people in the humid regions.

Sun hot July 20


High nighttime temperatures allow the heat to build at an even faster pace the next day and overnight humidity levels can be significantly higher than they are in the afternoon as a result.

In some of the major cities, temperatures may not drop below 80 at night in the heat wave.

Why the heat is no laughing matter

In the forecast conditions, perspiration fails to evaporate quickly and the body temperature can climb significantly, followed by heat exhaustion and heat stroke.

Heat kills more people on an annual basis than any other weather-related factor.

Weather Fatalities


Until the pattern breaks, strenuous physical exercise and manual labor should be limited. If these activities must take place, they should be avoided during the hottest part of the day and frequent breaks from the heat are highly recommended.

Remember to increase the intake of non-alcoholic fluids and frequently check on young children and the elderly.

Avoid walking pets and barefoot on paved and concrete areas during the late morning and afternoon hours as these surfaces can become hot enough to cause severe burns to paws and feet.

When will the heat wave break?

An upcoming pattern flip is in store that will allow cooler and less humid air to push southward from Canada.

The jet stream pattern is forecast to make a major change after this weekend. The jet will shift southward in the Central and Eastern states and bulge northward in the West this week.

this Week US Jet


"That will allow much more comfortable air to gradually sweep across the nation's midsection and the Northeast through early week," according to AccuWeather Senior Meteorologist Kristina Pydynowski. "However, residents will face more damaging thunderstorms and flooding downpours before the heat releases its grip."

The cold front ushering in the more comfortable conditions may even press southward to the I-20 corridor in the South at midweek.

Since it may not entirely clear the Deep South, the front may result in an extended stormy time across the region this week.

Download the free AccuWeather app for more details on temperature trends in your community. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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