Americans are warned to brace for below-freezing temperatures with a 20-degree swing in some areas after weeks of spring-like warmth

Millions of Americans have enjoyed weeks of spring-like warmth only to find themselves bracing for below-freezing temperatures, with some areas experiencing a 20-degree swing.

After St. Patrick's Day weekend, much of the country will be plunged into chilly weather, with more than half of the US population facing cold or even freezing conditions.

The cold air is forecasted to creep into the Midwest on Sunday, with temperatures dropping to 23 degrees in Minneapolis and 31 degrees in Chicago.

This wintry weather will extend into Tennessee and Alabama in the South before eventually reaching the Northeast. New York City, for example, is set to see a low morning temperature of 35 degrees on Tuesday morning.

According to Fox Weather, about 182 million Americans are expected to experience below-average temperatures on Monday.

Millions of Americans have enjoyed weeks of spring-like warmth only to find themselves bracing for below-freezing temperatures, with some areas experiencing a 20-degree swing

New York City  is set to see a low morning temperature of 35 degrees on Tuesday morning after a week of spring-like warmth. Pictured: people enjoy the warm weather in Central Park on Thursday 

Some cities are set to experience a swing of more than 20 degrees after weeks of spring-like warmth. Pictured: people enjoy the warm weather in Central Park on Thursday

From Saturday to Monday, St. Louis in Missouri is anticipating a swing of more than 20 degrees, with temperatures dropping from the high 60s to the low 40s. 

Similarly, Atlanta's high temperature is expected to drop from the low 70s to the mid-50s, according to CNN.

Minnesota residents may wake up to a typical winter weather, with morning temperatures as low as 23 degrees on Sunday and dropping below 20 degrees on Monday.   

Temperatures will be low enough to bring frost and freeze conditions all the way into the South as both Louisville and Nashville on Monday morning could drop into low 30s, a typical winter weather in the area. 

Further progressing eastward, the cold air is expected to reach much of the eastern half of the country by Monday. 

For instance, New York City is forecasted to see days with high temperatures ranging from the mid- to upper 40s, compared to the historical average of 50 degrees.  

Waves of colder air could trigger flurries and snow squalls in parts of the Midwest and Northeast, AccuWeather Meteorologist Ryan Adamson said. 

 'The situation is a bit more complex than last weekend as there will be some disturbances riding along with the jet stream dip and these will cause the extent of the flurries and snow showers to fluctuate,' he added. 

The arrival of cold early spring weather comes after many parts of the country saw the warmest winter on record. 

Record-breaking heat swept the nation in February, traditionally one of the coldest months of the year. 

Nebraska and Illinois experienced temperatures in the 60s and 70s despite their average February temperatures being in the high 30s to low 40s. 

According to the National Weather Service, Nebraska had its 'second warmest February on record in its 154-year history of tracking weather. 

FOX Forecast Center meteorologist Cody Braud blamed EL Nino for the warm winter, saying the weather pattern 'played a large role in the record heat.' 

The arrival of cold early spring weather comes after many parts of the country saw the warmest winter on record. Pictured: people enjoy the warm weather in Central Park on Thursday

FOX Forecast Center meteorologist Cody Braud blamed EL Nino for the warm winter, saying the weather pattern 'played a large role in the record heat' Pictured: Hurricane Irma seen in Miami with EL Nino blamed for the gray skies 

El Niño - which translates to 'little boy' in Spanish - is caused by a shift in the distribution of warm water in the Pacific Ocean around the equator. Pictured: People walk along Times Square amid a winter storm in February 

'The pattern for El Niño typically means a strong Pacific jet, which displaces the polar jet farther to the north,' he said. 

'There are obviously other facets to the story, but this largely keeps the coldest air trapped out of the Lower 48.' 

'This allowed an abundance of warm air to dominate the eastern two-thirds of the country. Not only that, but it was allowing storms to be mainly rain.' 

El Niño - which translates to 'little boy' in Spanish - is caused by a shift in the distribution of warm water in the Pacific Ocean around the equator. 

Although the pattern's influence has been weakening, the NOAA warns it could hold on through the summer, bringing above-average temperatures through August. 

By the end of next week, temperatures will rebound quickly, with the remaining spring months skewing warmer than usual, according to the Weather Channel. 

'​April and May may be only moderately anomalously warm, which would be notable in our new world of accelerated global warming,' according to Todd Crawford, Vice President of Meteorology at Atmospheric G2.