Severe weather is hitting parts of the central United States causing dangerous conditions with authorities issuing warnings about the phenomenon.

Snow and ice have covered major roads in nearly all of Kansas, western Nebraska and parts of Indiana, where the state National Guard was activated to help stranded drivers. Snow is expected to reach at least 8 inches, particularly north of Interstate 70, and the National Weather Service has issued blizzard warnings for Kansas and Missouri. The warning was extended to New Jersey for Monday and early Tuesday.

A state of emergency has been declared in Washington, D.C., which is expected to last at least until the end of the day on Sunday.

“For locations in this area that have the highest snow levels, it could be the heaviest snowfall in at least a decade,” the weather service said early Sunday.

About 63 million people in the U.S. have received weather alerts, said Bob Oravec of the National Weather Service.

In Indiana, snow covered parts of Interstate 64, Interstate 69 and US Route 41, with authorities urging people to avoid those roads.

“It’s snowing so hard, the snowplows are coming through and then within half an hour the roads are completely covered again,” they said in a news release.

Part of I-70 was closed in central Kansas until Saturday afternoon. About 8 inches of snow had fallen in parts of the state, with more than 10 inches expected in parts of Kansas and northern Missouri.

Parts of New York state saw up to 3 feet (0.9 m) of snow, and the bad weather is expected to last until late Sunday afternoon.

The storm will then move into the Ohio Valley and reach the Mid-Atlantic states on Sunday and Monday, with heavy frost expected as far south as Florida.

The National Weather Service warned that travel in many states, including Kansas and Missouri, could be “very difficult to impossible.”

The bad weather caused more than 3,300 delays and 1,700 cancellations to and from the US on Sunday, according to the BBC. Kansas City International Airport has been hardest hit for outbound flights, with 86% of them canceled. For inbound flights, St. Louis Lambert International Airport in Missouri tops the chart, with 53% of flights delayed and 7% canceled as of 10:20 a.m. local time.