U.S. power prices soared to their highest since the winter as homes and businesses cranked up their air conditioners to escape a brutal heat wave blanketing the eastern half of the country, stressing regional power grids.

Extreme weather reminds consumers of the fatal freeze in February 2021 that left millions of Texans without power, water and heat for days and a brutal heat wave in August 2020 that forced the California power grid to impose rotating outages that affected about 800,000 customers over two days.

Meteorologists at weather forecaster AccuWeather projected high temperatures in New York, the biggest city in the United States, would tie the 137-year-old record of 96 Fahrenheit (35.6 Celsius) on Monday before breaking that record on Tuesday with the mercury expected to reach 98 F.

After that, however, the weather in New York is expected to cool rapidly from 94 F on Wednesday to 85 F on Thursday and 78 F on Friday.

That compares with current record highs of 96 F for both Monday and Tuesday set in 1888 and a normal high in New York of 82 F at this time of year.

Next-day power prices at the PJM West hub in Pennsylvania soared by over 430% to around $211 per megawatt hour (MWh), their highest since January.

In New England, meanwhile, power prices jumped by over 180% to around $161 per MWh, their highest since February.

That compares with power price averages of $55 per MWh in PJM and $81 in New England so far in 2025.

Hot Weather Alerts

PJM Interconnection, which operates the power grid in all or parts of 13 states from New Jersey to Illinois, issued an alert for Monday asking power generators to be ready to operate at maximum capacity if needed during the heat wave.

PJM said it expected power demand to reach 160,000 megawatts (MW) on Monday, 158,000 MW on Tuesday and 155,000 MW on Wednesday.

One megawatt can power about 800 homes on a normal day but much fewer on a hot summer day when homes and businesses crank up their air conditioners.

The alert is aimed at transmission and generation owners who can schedule maintenance work accordingly, and also signals to neighboring regions that PJM power exports may need to be curtailed, the grid operator said.

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(Reporting by Scott DiSavino in New York and Ishaan Arora in Bengaluru; Editing by Jan Harvey and Andrea Ricci)