Chicago, Feb 01 (Agencies):  A severe storm poses serious menace for 100 million already winter-weary people in US and may dump mounds of fresh snow, sleet and ice on them as it barrels eastward across the United States.

Roaring winds and freezing rain threatened to turn roads into deadly ice rinks and knock down trees and power lines and forecasts warned of dangerously cold temperatures.

Warnings of blizzard, winter storm and freezing rain were flashed for more than 25 states, from North Dakota and Colorado down to New Mexico, then up through Texas, Kansas and Missouri to the Great Lakes region and across Pennsylvania to New England.

The Federal Emergency Management Agency (FEMA) urged residents to brace up for the fury of the storm.

"A storm of this size and scope needs to be taken seriously," said FEMA Administrator Craig Fugate, who warned that "it's critical that the public does its part to get ready."

Fugate urged residents in storm affected regions to "check on your neighbours, especially the elderly and young children -- those who can be most vulnerable during emergencies."

Schools and government offices were closed on Tuesday as freezing rain began to fall.

Airlines warned of delays and cancellations, offering customers a chance to rebook flights at no fee.

 The worst of the storm is expected on Tuesday afternoon and evening as a large amount of moisture sucked up from the Gulf of Mexico feeds the huge system and is transformed into snow and thunderstorms.

Wind chills were forecast to go down to 30 to 50 below in Colorado, Wyoming, the Dakotas, Kansas, Idaho and even parts of Texas.

Officials cautioned the public to stay at home rather than try to go out in the crippling and potentially record-breaking storm.