The cold air invaded the northwestern U.S. during New Years day and was accompanied by accumulating snow to near sea level in Washington. Cold air will hang on much of the week in the Northwest.

Over the Southwest, including Southern California and southern Arizona, the chilly weather will continue into Thursday, as temperatures will moderate late in the week. Cold air will hang on much of the week in the Northwest.

"The main thrust of the cold air will extend from the northern Rockies to the northern Plains and the Upper Midwest," according to AccuWeather Meteorologist Evan Duffey.

By the middle of the week, actual temperatures will bottom as low as 20 degrees Fahrenheit below-zero and will rival the coldest air of the season so far over the northern tier of the Central states. AccuWeather RealFeel® Temperatures over part of the northern Plains and Rockies can dip as low as minus 40 for a time.

Cold air will sweep to the Atlantic coast and will penetrate into part of the Deep South.

People in the Chicago area will endure several days with highs in the teens and low temperatures in the single digits from Wednesday through Saturday. Temperatures at these levels are 15 to 20 degrees below average even for January.

"Even though the cold air will moderate by the time it gets to the Southern and Eastern states, it will still pack a punch," Duffey said.

For example, in Pittsburgh, following temperatures surging to near 50 during Tuesday evening, temperatures will fall through the 30s and 20s on Wednesday to the teens by Thursday morning. Factoring in wind and other conditions, RealFeel temperatures will plunge to near zero at times on Thursday. It will feel 50 to 60 degrees lower on Thursday morning, when compared to Tuesday evening.

As the cold air pushes into the Northeast on Thursday and Friday, there is the chance for some moisture to be drawn up from the South, bringing a period of light snow or flurries.

But despite the moisture, cold will persist.

AccuWeather interactive temperature maps

Around New York City, high temperatures may struggle to get much past the freezing mark this weekend.

In the Atlanta area, high temperatures in the upper 60s on Tuesday will be replaced with highs in the 40s on Friday. Depending on the track of a storm from California and possible wintry precipitation temperatures reach no higher than the 30s this weekend.

Even in Houston and New Orleans, temperatures will be slashed by 20 to 25 degrees from their early-week highs.

Over the Florida Peninsula, the arrival of the cooler air will come in stages. Temperatures will be trimmed back to slightly above normal by the end of the week. In Orlando, this will translate to highs in the lower to middle 70s. However, a second push of cold air will produce highs in the upper 50s to near 60 by Sunday.

"Even though it will get cold over the interior South, we do not expect a freeze in the active growing areas of Southern California, Texas, Florida and Louisiana with this air mass," Duffey said.

Temperatures will moderate from west to east during the second week of January.

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