At least 13 are dead after a major storm pounded eastern parts of the United States last Friday.

The storm also knocked out power in more than three million households in Ohio, Virginia and Maryland amid a scorching heat wave.

Afternoon highs in Washington and surrounding areas hit by the storm surged over 38 degrees Celsius on Sunday.

Environmental authorities issued a “Code Purple” air quality emergency which is declared when the quality of air is extremely poor.

Electric power authorities have estimated that it would take up to a week to restore power in some of the storm-hit areas.

U.S. President Barack Obama authorized the Federal Emergency Management Agency to manage all disaster relief efforts in Ohio, which was hit hardest by the storm.