Philadelphia-area residents woke up to spring-like temperatures this morning, but that warmth is about to turn to potentially record-breaking cold.
The temperature at Philadelphia National Airport had reached 59 degrees by 6 a.m. In the next 24 hours, the mercury will drop 50 degrees, forecasters say.
The National Weather Service says to expect low temperatures in the single digits -- likely around 8 or 9 degrees -- overnight into Tuesday morning. And the high Tuesday is expected to reach just 12 degrees in Philadelphia.
Those temperatures could set new records. The lowest ever recorded temperature for Jan. 7 in Philadelphia is 7 degrees, and lowest maximum temperature for date is 20 degrees.
The wind will bring an added chill Tuesday, with 15 to 20 mph winds expected, and gusts of up to 35 mph. Expect wind chill values as low as 13 below in Philadelphia, and as low as minus 30 farther north in the Poconos, the weather service says.
Wind speeds should decrease gradually Tuesday night into Wednesday and the temperature will rise, though Wednesday is also expected to be cold. Forecasters expected wind chill values as low as 8 below in the morning, with highs in the 20s expected for the afternoon.
The arctic-like blast comes as a low pressure system and associated cold front moves in from the Midwest eastern Great Lakes region.
The cold and potentially dangerous wind chills will affect much of the United States, the National Oceanic and Atmospheric Administration says. Nearly the entire country --including areas as far south as Texas and Florida -- is expected to see sub-freezing temperatures.
As many as 117 million people are under wind chill warnings, advisories and watches, according to the Red Cross.
The widespread cold accompanies a storm that dumped snow on the Midwest, where frigid temperatures are already in place.
Crane Lake, Minn., has posted the lowest temperature in the country over the past 24 hours, according to AccuWeather: The mercury has dropped to minus 38. And in Chicago, the temperature began falling by about two degrees an hour from midnight through this morning, the Chicago Tribune reports, reaching minus 12 by 5:30 a.m. and hitting a record low of minus 16 around 8 a.m.
The cold coming east could "bring the coldest temperatures some have experienced in 20 years," AccuWeather says.
The weather service warned of several problems the frigid temperatures could spur: Standing water will freeze tonight, as the temperature drops, and roadway chemicals become less effective in the cold. Water pipes could freeze and burst amid the very low temperatures expected Tuesday and Wednesday mornings.
And the weather is already causing problems for travelers: All flights at Philadelphia International Airport were stopped for part of the morning due to wind, and the airport was reporting numerous delays and cancelations.
Peak wind gusts at the airport this morning reached 45 mph, the weather service said.
Contact Emily Babay at 215-854-2153 or firstname.lastname@example.org. Follow @emilybabay on Twitter.
Contact the Breaking News Desk at 215-854-2443 or BreakingNewsDesk@philly.com. Follow @phillynews on Twitter.