A massive winter storm covering nearly 2,735 km has brought Arctic cold, record snowfall and blizzard conditions to a huge swathe of the US.

Winter weather warnings have been issued from south western Utah, across the Rocky Mountains and Great Plains to north eastern Michigan.

In California parts of the Sierra Nevada saw up to 1.2 metres of snow and in Arizona the storm brought high winds to the Phoenix are, leaving 250,000 people without power as power lines were felled.

Colorado is experiencing blizzard conditions while the Denver area, up until now spared significant snowfall, suffered through single digit temperatures and wind chills dipping to10 degrees below zero.

Two people were killed in New Mexico due to traffic accidents on dangerously icy roads as the state struggled to clear heavy snow falls.

The storm is moving east over the Rocky Mountain region and is forecast to intensify, causing extensive travel problems.

Snowfalls of up to 38cm are forecast across states in a line from Nebraska to Michigan.

Similar conditions are forecast for an area from Nebraska to Madison, Wisconsin and all points in between.