(Bloomberg) — Temperatures will soar across Texas this week, further testing the state’s electrical grid as households and businesses switch on air conditioners to get relief from record seasonal highs.

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The heat will also spread across the US Midwest and Northeast, with the potential for record warm overnight low temperatures from Philadelphia to Boston. Still, it’s Texas — whose energy network has faltered during harsh weather in the past — that’s in the spotlight. The Electric Reliability Council of Texas has warned that the state’s grid will face extreme weather risks as the situation unfolds across the US.

US grids are already experiencing stress and it’s not even summer — the period when electricity demand soars and consumption tends to touch annual highs. The early arrival of hotter temperatures is taxing power-generating assets when many power plants are offline for repairs and upgrades ahead of the peak summer season. Swaths of the US — from Texas and the Southeast to the Midwest and New England — face supply crunches in the sustained searing heat, according to the North American Electric Reliability Corp.

Southern parts of Texas are forecast to see temperatures above 100F (38C) in the coming days, the National Weather Service said. When combined with humidity, it will feel closer to 110F or more in many places. Temperatures will push deeper into the 90s by this weekend in Houston, where more than 73,000 homes are still without power after last week’s windstorm, according to PowerOutage.us.

Read More: Houston Storm Hit Most-Stressed US Grid With Outages in Thousands

Electricity usage is projected to repeatedly hit record May highs in the coming days, climbing to more than 77 gigawatts next Monday, according to forecasts from the state grid operator. Expectations of soaring demand and a high number of plant outages amid seasonal maintenance prompted Ercot to issue an operating condition notice for Friday through Monday — the first level of communication of a possible emergency condition. The riskiest period is around sunset because plunging solar generation has to be quickly replaced by power from gas plants and batteries.

The heat in Texas will build through the week an likely last into June, said Bob Oravec, a senior branch forecaster with the US Weather Prediction Center.

“It actually gets hotter with time,” he said. “There is nothing to change the weather pattern, it looks like it is going to be prolonged heat.”

In addition to the heat, more than 10 million people in parts of Texas — including Dallas, Arkansas, Oklahoma and Louisiana — are bracing for storms, with enhanced risk of high winds, hail, downpours and tornadoes on Wednesday. A larger area from Texas to the Great Lakes and western New York has a slight risk of experiencing these conditions.

A pattern of extreme weather has been pounding the central US for weeks, including a type of windstorm known as a derecho that battered Houston and spread damages as far east as Florida. On Tuesday, there were 20 reported tornadoes, 244 high wind reports and 86 instances of hail across the US, the Storm Prediction Center said, with most of them in upper Midwest.

(Updates with electricity demand forecasts from Texas in fifth paragraph.)

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