CHICAGO (NewsNation Now) — A frigid blast of winter weather across the U.S. plunged Texas into an unusually icy emergency Monday that knocked out power for more than 4 million people, shut down grocery stores and air travel, and sent cars skidding on dangerously snowy and slick roads.

As nightfall threatened to plummet temperatures again into single digits, officials warned that homes still without power would likely not have heat until at least Tuesday, as frustration mounted and the state’s electric grid came under growing demand and criticism.

“Things will likely get worse before they get better,” said Harris County Judge Lina Hidalgo, the top elected official in the county of nearly 5 million people around Houston.

Law enforcement reported two men were found dead along Houston-area roadways. Causes of death were pending, but officials said the subfreezing temperatures were likely to blame.

The worsening conditions halted the delivery of new COVID-19 vaccine shipments. Massive power outages across Houston included a facility storing 8,000 doses of Moderna vaccine, and health officials scrambled to find takers at the same time authorities were pleading for people to stay home.

The largest grocery store chain in Texas, H-E-B, closed locations around Austin and San Antonio, cities that are unaccustomed to snow and have little resources to clear roads. The slow thaw and more frigid lows ahead was also taking a toll on Texas’ distribution of COVID-19 vaccines.

State health officials said Texas, which was due to receive more than 400,000 additional vaccine doses this week, now does not expect deliveries to occur until at least Wednesday.

According to the National Weather Service, a coast-to-coast winter storm extending across the Great Plains and down into the Deep South could cause a cold snap unlike anything seen since 1905.

Forecasters said an Arctic air mass is spreading southwards, well beyond areas accustomed to freezing weather, with winter storm warnings posted for most of the Gulf Coast region, Oklahoma and Missouri.

By Monday afternoon, the NWS said record low temperatures have already been reported across the country. The weather station in Hibbing/Chisholm, Minnesota, saw a record low of -38 degrees, while lows were also reported from Sioux Falls, South Dakota, at -26 degrees, and Valentine, Nebraska, at -33 degrees, down to Dallas, Texas, at 7 degrees.

Forecasters expect many of the locations that are recording new low temperatures Monday to experience even colder weather by Tuesday morning.

Across the Chicago area, dangerous wind chills in the -15 to -25-degree Fahrenheit range are forecast to continue Monday, NewsNation affiliate WGN reported. The city is warning residents that 8-12 inches of snow was expected through Tuesday.

In Dallas, the low could drop to just 1 degree Monday. The weather has prompted a power emergency in Texas, where rotating power outages were initiated by the Electric Reliability Council of Texas. It’s left more than 2 million customers without electricity.

President Joe Biden also declared an emergency in Texas in a statement Sunday night. The declaration is intended to add federal aid to state and local response efforts.

Now Texas power providers and the council that manages the power flow in the state are facing national criticism, as planned rolling blackouts in Austin have led to outages lasting for hours, NewsNation affiliate KXAN reported.

In Kansas, Gov. Laura Kelly declared a state of disaster as frigid temperatures and life-threatening wind chills grip the state.

Wind chills dropped as low as -30 Fahrenheit in some areas overnight Sunday and temperatures will struggle to be above zero, adding to nearly a week of extremely low temperatures in much of the state, the National Weather Service said.

The low temperatures put stress on utility and natural gas providers, which were asking customers to conserve energy during the cold snap. The emergency declaration allows for state resources and personnel to be used to help with response or recovery operations under certain circumstances.

Meanwhile, winter storm warnings blanketed most of Louisiana and Mississippi and extended into parts of Alabama, where forecasters warned of the possibility of ice storms in the northwest corner of the state, according to the National Weather Service.

In Louisiana, a 50-year-old Lafayette Parish man died after slipping on ice and hitting his head on the ground, according to the Louisiana Department of Health. The coroner confirmed the death as storm-related.

Louisiana State Police said Monday morning on Facebook that they had investigated nearly 75 weather-related crashes in the previous 24 hours as a mixture of snow, sleet and freezing rain created treacherous conditions. As the weather continued to deteriorate across the state and with temperatures remaining at or below freezing, ice was accumulating on the roadways and troopers urged drivers to stay off the roads.

“We already have some accidents on our roadways,” Kentucky Gov. Andy Beshear said during a morning news conference. “It is slick and it is dangerous.”

Slick conditions also plagued Mississippi, where the state Department of Transportation was reporting ice on roads and bridges throughout much of the state. The agency posted photos and video of snowy interstates on Facebook and urged people to stay home so crews can work to clear the roads.

Air travel was also affected. By midmorning, 3,000 flights had been canceled across the country, about 1,600 of them at Dallas/Fort Worth International and Bush Intercontinental airports in Texas. At DFW, the temperature was 4 degrees Fahrenheit — 3 degrees colder than in Moscow.

In Houston, officials said Bush Intercontinental Airport runways would remain closed until at least 1 p.m. Tuesday, a day longer than previously expected.

The Associated Press, Reuters and NewsNation affiliates WGN, WKRN and KXAN contributed to this report.