Across the country, it is the same, sweaty story. On Sunday, two million people across the mid-Atlantic were left stewing in nearly 100-degree heat with no electricity after deadly thunderstorms toppled trees and power lines. Officials warned that the high heat could fuel more severe thunderstorms this week.

Image Since last week, Hill City has cooled off to the low 100s. Credit... The New York Times

“There is a significant risk of additional storms that could lead to additional outages, so there is a possibility that the situation could deteriorate in the coming days,” Gov. Bob McDonnell of Virginia said during a conference call with reporters. “This is going to be a multiday recovery event with dangerously high heat, so everyone needs to remain vigilant.”

Utility companies said it might take a week to restore power completely in some places.

Officials throughout the region opened air-conditioned libraries and community centers to provide some relief for residents without power. Grocery stores reported runs on ice, water and nonperishable foods. Harris Teeter, a regional grocery chain, quickly went through 25,000 bags of free ice it was dispensing at stores in Northern Virginia and Maryland.

In parts of Georgia and Tennessee, the air quality was so bad over the weekend that officials scrapped their Code Red warnings and dubbed the steamy haze a Code Purple, signaling very unhealthy air.

In New York, temperatures parked in the muggy 90s have baked the streets and turned subway tunnels into stifling saunas. Farmers in the Midwest are watching helplessly as ovenlike conditions blister their runty fields of corn.