(Reuters) - More than 1.4 million people from Illinois to Virginia remained without power Tuesday morning after the weekend's violent storms, and a heat wave continued to bake much of the region, the regional power companies said.

The power companies warned some customers could be without power to run their air conditioners for the rest of the week in the worst hit areas.

High temperatures across the region were expected to reach the 90s Fahrenheit (32 Celsius) over the next several days, according to AccuWeather.com.

The storms crossed the Eastern United States with heavy rain, hail and winds reaching 80 miles per hour starting Friday night, leaving more than 3 million homes and businesses without the power, according to a federal energy report.

The storms also claimed at least 15 lives, mostly from falling trees and branches across the Midwest and Mid-Atlantic states.

American Electric Power Co Inc of Ohio said Tuesday morning that crews were working to restore power to 357,000 customers in Virginia and West Virginia; 298,000 in Ohio; 32,000 in Indiana; and 14,000 in Kentucky.

FirstEnergy Corp of Ohio said it had 216,000 customers out in its five-state service area of Ohio, Pennsylvania, West Virginia, Maryland and New Jersey. That was down from about the initial 566,000 affected by the storms.

Illinois-based Exelon Corp said its Baltimore Gas & Electric (BG&E) unit in Maryland had about 170,000 customers out, down from about 600,000 homes and businesses affected.

Virginia power company Dominion Resources Inc said it still had more than 170,000 customers without electricity in its Virginia and North Carolina service areas.

Washington, D.C.-based Pepco Holdings Inc said it had more than 116,000 customers without power in the District of Columbia and Maryland and more than 69,000 out in New Jersey.