Winter storm updates: Dozens dead across US in wake of massive snowfall, deep freeze

New York City public schools will be closed on Monday due to the storm, with students attending remote learning instead.

The winter storm on Sunday was wreaking havoc on electrical grids across several states, including Texas and Tennessee.

As of 9 a.m., more than 730,000 utility customers across the country were without power, according to PowerOutage.us.

Power outages were affecting more than 244,000 utility customers in Tennessee, 134,000 customers in Texas, 123,000 customers across Mississippi, nearly 120,000 in Louisiana, and nearly 40,000 customers in Kentucky, according to PowerOutage.us.

-ABC News' Jessica Gorman and Alexandra Fine

At least 299,815 customers were without power across the U.S. as of early on Sunday morning, according to data from PowerOutage.us.

The worst-affected state was Texas, where more than 82,000 customers were without power. More than 80,000 customers in Mississippi were also without power, the online tracker said.

Also without power were more than 71,000 customers in Louisiana, more than 24,000 customers in Tennessee and more than 16,000 customers in New Mexico.

-ABC News' Juwon Funes

At least 20 states have declared a state of emergency as the storm nears: Alabama, Arkansas, Delaware Georgia, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Tennessee, Texas and Virginia.

Washington, D.C., has also declared a state of emergency.