polar vortex

Erin Stevenson O'Connor / Flickr Creative Commons

Gov. Mary Fallin has issued an executive order declaring a state of emergency to deal with a dwindling supply of propane in Oklahoma.

The order issued on Tuesday waives certain licensing requirements and other restrictions for those transporting propane in the state.

The brutally cold polar air that has descended across the United States has led to a spike in demand for propane, which an estimated 400,000 residents use to heat their homes, especially in rural areas.

The deaths of at least 21 people are now being blamed on the winter storms and severe cold weather that have gripped much of the nation since late last week, The Associated Press reported early Wednesday.

At least half have been attributed to weather-related traffic accidents. The wire service adds that:

outdoor thermometer in single digits
RiverRatt3 / Flickr Creative Commons

Dozens of schools across Oklahoma called off classes as bitterly cold sub-zero temperatures and wind chill indexes were reported.

The Oklahoma City and Tulsa school districts - the state's two largest - are among those cancelling classes for Monday.

The National Weather Service issued a wind chill warning for Ottawa and Craig counties until noon Monday and a wind chill advisory for all but far southern and parts of southwestern Oklahoma.

One weather map tells the story.

Check out the National Weather Service's map of the Lower 48 for Monday night. If you need to know just how much of the nation's going to be freezing (or well below!), it offers a bone-chilling picture. Anywhere in the blue-to-purple shades is going to be cold — and that's before accounting for wind chills.

What is the Weather Service forecasting?