Nearly 200 million people in US: Dangerous heat is forecast to “engulf” much of the eastern half of the United States as extreme temperatures spread from the Midwest into the Northeast and mid-Atlantic where some residents will see their hottest temperatures of the year, according to the National Weather Service.

Althouth much of the country does not cool much on normal summer nights, night temperatures are forecast to stay hotter than usual leading to excessive heat warnings from the Plains to the East Coast.
On Thursday nearly 200 million people in the United States, or 60% of the U.S. population, were under a heat advisory or flood warning or watch, but moisture moving into the Southwest has reduced the area of excessive heat warnings to the southernmost counties of California and parts of southern Arizona.

On top of the heat, severe thunderstorms are forecast for parts of the Great Lakes and Ohio Valley, west to the Middle Missouri Valley through Saturday morning.

Scientists have long warned that climate change, driven by the burning of fossil fuels, will lead to more and prolonged bouts of extreme weather.

The prediction for continued excessive heat comes a day after the World Meteorological Organization and the European Union’s Copernicus Climate Change Service declared July 2023 the hottest month on record.

On Thursday, heat and humidity in major cities along the East Coast, including Washington, D.C., Philadelphia and New York City, created a real feel above 100 degrees Fahrenheit (37.8 degrees Celsius). Forecasters expect several records may break Friday with temperatures 10 to 15 degrees Fahrenheit (5.5 to 8 degrees Celsius) above average.

In the Southwest and southern Plains, oppressive temperatures have been a blanket for weeks. One meteorologist based in New Mexico called the prolonged period of temperatures over 100 degrees (37.8 C) unprecedented.

“They probably aren’t going to have a lot of sympathy for the rest of the country,” said Bob Oravec, lead forecaster with the National Weather Service’s Weather Prediction Center.

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Due to the extreme heat, some of the nation’s large power grids and utilities are under stress, which could affect Americans’ ability to cool off.

In New York City, utility Con Edison sent out a text blast asking residents to be frugal with air conditioning to conserve electricity. Overtaxing an electrical grid can mean blackouts, which are not just an inconvenience, but can lead to equipment failures and major pollution as equipment restarts.

The country’s largest power grid, PJM Interconnection, declared a level one energy emergency alert for its 13-state grid on Wednesday, meaning the company concerned about ability to provide enough electricity.

“PJM currently has enough generation to meet forecast demand, but operators continue to monitor the grid conditions for any changes,” said spokesperson Jeffrey Shields.

PJM isn’t the only electrical grid to issue such an alert. The Midcontinent Independent System Operator, which mostly covers states in the Midwest and Northern Plains, issued a similar one on Thursday.

The California Independent System Operator also issued an energy emergency alert for the evening on Wednesday, in part due to excess heat in Southern California, but it expired the same day. Anne Gonzales, a CAISO spokesperson, said they expect to be able to meet demand the next few days.

And a spokesperson for the Electric Reliability Council of Texas, which covers most of Texas, said they expect their grid will operate per usual during this latest blast of extreme weather across the country.

The dangerous heat peaks in the Northeast, mid-Atlantic, and Midwest Friday and Saturday before a cold front is expected to bring some relief Sunday and into next week.