A “heat dome” gripping much of the eastern United States has driven temperatures close to 40 degrees Celsius and caused a sharp rise in electricity prices, straining power infrastructure ahead of the July 4 holiday weekend. The National Weather Service issued extreme heat warnings for an estimated 130 million people on Thursday, with more than 150,000 households across the Northeast, Midwest, and South experiencing power outages.

Across the eastern US, temperatures climbed to as high as 37.7 degrees Celsius, with parts of the Southwest also affected. The dangerous heatwave was expected to persist through the weekend, raising concerns about public health and energy supply. Utilities and grid operators reported surging demand as many customers increased air conditioning use, leading to significant price spikes in wholesale electricity markets.

Data from the Energy Information Administration showed wholesale spot electricity prices in New England surged over 240 percent, while prices in New York City roughly doubled. The Midwest saw increases exceeding 50 percent. Industry experts pointed to the basic economic principle of supply and demand amid limited electricity supply to explain the price jumps. Mark Dyson, a managing director at the Rocky Mountain Institute, emphasized that the spike reflected the scarcity of resources meeting unprecedented demand during the heatwave.

Consolidated Edison, the primary utility serving New York City, responded to the surge by reducing voltage by about 8 percent in parts of the Bronx and Manhattan, urging customers citywide to conserve energy. New York Mayor Zohran Mamdani asked residents to set air conditioning thermostats to 78 degrees Fahrenheit (approximately 25.5 degrees Celsius) and delay using energy-intensive appliances such as dishwashers and laundry machines until later in the day.

The mid-Atlantic and much of the Midwest are served by PJM Interconnection, a regional transmission organization that reported a record-high net load on its grid on Wednesday evening. On Thursday, PJM indicated it might restrict electricity exports to neighboring regions to manage supply constraints. Calvin Butler, CEO of Exelon—the largest U.S.-based utility serving customers—highlighted that rising electricity demand is outpacing the introduction of new energy resources, posing long-term challenges to grid stability.

Duke Energy, which operates in states including North and South Carolina, announced it would activate demand-response programs, incentivizing customers to reduce electricity usage temporarily to alleviate pressure on the grid.

The ongoing heatwave and related electricity supply challenges underscore growing concerns about energy affordability for Americans, who have already faced elevated costs for fuel and food in recent months. Utilities and officials continue urging residents to adopt energy-saving measures to help balance demand during the extreme weather event.