The map above, from weather information service Intellicast.com, shows the temperatures forecast in the USA at 6.45am ET (11.45am GMT). 

Temperatures are as low as double digits in the coldest parts of northeastern USA, but the wind chill maps show that it will feel even colder. 

The wind chill forecast for 10am ET show that in the most extreme cases it could feel as cold as -50C.   

The deep freeze comes after a powerful snowstorm, known as a bomb cyclonee, unleashed blizzards and heavy snow on the USA East Coast this week. 

The cold and snowy weather have been blamed for at least 18 deaths in the past few days, including four in North Carolina traffic accidents. Three homeless people died in Texas.

From northern Florida up through New York City into New England, tens of millions of people will be under wind chill and freeze warnings throughout the day.

Temperatures in some parts to the north were expected to be -40F (-40C), while in parts of the south highs were forecast to be 20 degrees below average.

"It can be very dangerous," said Dan Pydynowski, a meteorologist with private forecasting service AccuWeather. "Any kind of exposed skin can freeze in a couple of minutes."

To find out the lowest temperatures in the USA right now, you can visit the interactive temperature map on the Intellicast.com website. 

A WXCharts map shows the extreme cold airmass affecting eastern North America but clearing into the Atlantic next week. 

The interactive weather data viewer service added: “Anomalous warmth then spreads from the west late week, replaced by a new cold plunge from the northwest.”

The National Weather Service (NWS) said the latest arctic surge has brought freezing temperatures to most places east of the Mississippi River. 

This afternoon high temperatures will likely be around 20 to 30 degrees below average across the northeastern USA, the Great Lakes, Ohio Valley and the Appalachians. 

The NWS said: “Readings in the teens are likely from Washington, D.C. up to New York City with single digits up into coastal New England. 

“Based on the latest forecasts, overnight temperatures should go below zero degrees over most of New England with perhaps even some 5 to 10 degree numbers all the way into North Carolina. 

“Suffice to say, it will be a brutally cold weekend but some relief is in sight heading into early next week.

“Until then, the frigid temperatures aloft should keep lake effect snow production going over the Great Lakes although amounts are much lighter than recent days.” 

The NWS said “While the eastern states remain frigid for another couple of days, mild conditions are in the forecast across the western and central United States.” 

Meteorologist Ryan Maue tweeted: “It has been very cold -- compared to the last 30-years -- and compared to history with many records SHATTERED.  

“Over the past 10-days (Dec 25-Jan 4), daily temperatures east of the Rockies have been 10°F to 25°F below normal centered on Midwest & Great Lakes & New England.”