ED Consolidated Edison Inc

By Scott Calvert and Keiko Morris 

A heat wave that gripped a large section of the U.S. set temperature records over the weekend from the Ohio Valley to the East Coast, but the power grid held up and forecasters said cooler, wetter weather was expected to begin arriving Monday.

About 72 million people were under excessive-heat warnings Sunday, down from about 128 million on Saturday, according to the National Weather Service. Temperatures on Sunday reached the upper-90s to around 100 degrees from eastern Kansas into the Ohio Valley and from the mid-Atlantic into parts of New England. Atlantic City International Airport in New Jersey saw 100 degrees, breaking the previous July 21 record of 99 degrees.

High humidity made it feel even hotter. The heat index on Sunday ranged from 105 to 110 degrees from North Carolina to Boston, said Jim Hayes, a weather-service meteorologist, and reached 112 in places.

"What made this situation unusual is the high humidity values," Mr. Hayes said.

Power companies in the greater New York City region had crews working over the weekend to respond to scattered outages. Consolidated Edison Inc., the utility that powers most of the city, expected a record for Sunday usage, eclipsing the record of 11,669 megawatts set Aug. 14, 2016, a spokesman said.

Despite huge demand, PJM, the power grid that serves parts of 13 states from Virginia to Illinois, said it saw no outages and no transmission issues over the weekend. A PJM spokeswoman said Saturday's peak load of 150,693 megawatts of electric demand appeared to be an all-time record for that day of the week.

A cold front will bring cooler air and rain starting Monday, and by Tuesday temperatures will be normal or below normal in much of the U.S. east of the Rockies. But Mr. Hayes said thunderstorms and damaging winds are likely from Tennessee to southern New England, and there is a heightened risk of flash flooding along the Interstate 95 corridor between Washington, D.C., and New York City.

Saturday's heat broke or tied records in a number of East Coast cities. Millinocket, Maine, reached 93 degrees, tying a record for the date. Manchester, N.H., set a record for the date of 97 degrees, breaking a mark set in 1949. And it hit 99 degrees at John F. Kennedy International Airport in New York, the highest on record for July 20.

At the same time, about 40 U.S. cities on Saturday tied or broke records for the highest minimum temperature on that date, as overnight temperatures remained in the high-70s or above 80 degrees across much of the Ohio Valley, mid-Atlantic and New England.

In Annapolis, Md., Saturday's sultry low of 84 degrees broke a record for July 20. On Saturday, New York's Central Park didn't get below 82 degrees. That tied the record-high minimum for the date and was two degrees below the warmest low temperature observed for any date since record-keeping began back in 1869: 84 degrees.

In New York City, emergency medical workers and firefighters faced a surge in calls during the weekend's extreme heat, city officials said. Calls for emergency medical services typically range between 4,000 and 4,500 on any day. On Friday, calls reached 4,606, and they soared to 5,143 on Saturday. As of noon Sunday, the city received 2,191 emergency calls.

Patients over 65 years old made up 70% of the 236 heat-related calls to 911 between Friday and noon on Sunday, a city official said.

Detainees in New York City jails were offered unlimited cool showers, water and ice. While most are housed in facilities with air conditioning, those without it had fans, a city spokeswoman said.

In Cincinnati, fans arriving at sweltering Great American Ball Park for Saturday evening's Reds-Cardinals baseball game heard a wintry mix of songs over the stadium sound system, including "Let It Snow," "Frosty the Snowman" and Foreigner's "Cold as Ice."

Aaron Sharpe, a DJ who picks the stadium's songs, said his instinct was to play heat-related songs -- but he decided to go cold. "These people are hot enough as it is, we don't need to remind them of that fact," he said.

Write to Scott Calvert at scott.calvert@wsj.com and Keiko Morris at Keiko.Morris@wsj.com

(END) Dow Jones Newswires

July 21, 2019 18:51 ET (22:51 GMT)

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