CHICAGO (NewsNation Now) — Winter weather that has overwhelmed power grids and left millions without electricity in record-breaking cold kept its grip on the nation’s midsection Wednesday.

At least 20 people have died, some while struggling to find warmth inside their homes. In the Houston area, one family succumbed to carbon monoxide from car exhaust in their garage; another perished after flames spread from their fireplace.

Blame the polar vortex, a weather pattern that usually keeps to the Arctic, but is increasingly visiting lower latitudes and staying beyond its welcome. Scientists say global warming caused by humans is partly responsible for making the polar vortex’s southward escapes longer and more frequent.

More than 100 million people live in areas covered Wednesday by some type of winter weather warning, watch or advisory, as yet another winter storm hits Texas and other parts of the southern Plains, the National Weather Service said.

NewsNation meteorologist Albert Ramon said the storm will move from Texas and Oklahoma Wednesday morning, to the Mid-South in the afternoon and then into the Northeast by the late evening.

The latest storm front was predicted to bring snow and ice to East Texas, Arkansas and the Lower Mississippi Valley before moving to the northeast on Thursday. Winter storm watches were in effect from Baltimore to Boston, and Texas braced for more icy rain and possibly more snow.

“There’s really no letup to some of the misery people are feeling across that area,” said Bob Oravec, lead forecaster with the National Weather Service.

Utilities from Minnesota to Texas and Mississippi have implemented rolling blackouts to ease the burden on power grids straining to meet extreme demand for heat and electricity as record low temperatures were reported in city after city.

More than 3.3 million customers remained without power by Wednesday at 1:30 p.m. EST in Texas, Louisiana and Mississippi; more than 200,000 were without power in four Appalachian states as well as in the Pacific Northwest, according to poweroutage.us, which tracks utility outage reports.

The weather has threatened the nation’s COVID-19 vaccination effort. President Joe Biden’s administration said delays in vaccine shipments and deliveries were likely.

White House COVID-19 coordinator Jeff Zients acknowledged Wednesday that the weather was impacting vaccine distribution, and some vaccination centers remained closed.

“People are working as hard as they can, given the importance of getting the vaccines to the states and to providers, but there is an impact on deliveries,” Zients said “What we’re encouraging governors and other partners to do is to extend hours once they’re able to reopen.”

The worst U.S. power outages by far have been in Texas, where officials requested 60 generators from the Federal Emergency Management Agency and planned to prioritize hospitals and nursing homes. The state opened 35 shelters to more than 1,000 occupants, the agency said.

Austin Energy said customers should be prepared to be without power for at least all day Wednesday, potentially longer. It also said Wednesday morning’s ice storm in the Austin area caused additional outages.

Texas’ power grid manager, the Electric Reliability Council of Texas, said electricity had been restored to 600,000 homes and businesses by Wednesday morning but that 2.7 million households were still without power.

Oklahoma’s largest electric utility reported no outages Wednesday, a day after rolling blackouts in and around Oklahoma City stopped electric-powered space heaters, furnaces and lights in minus-8 degree weather. But Oklahoma Gas & Electric warned customers of the potential for more short-term service interruptions due to the extreme cold and high demand for natural gas.

Nebraska also avoided another round of rolling power outages as subzero temperatures started to ease.

Entergy imposed rolling blackouts Tuesday night in Arkansas, Louisiana, Mississippi and Southeast Texas at the direction of its grid manager, the Midcontinent Independent System Operator, “as a last resort and in order to prevent more extensive, prolonged power outages that could severely affect the reliability of the power grid,” according to a statement from the New Orleans-based utility.

The Southwest Power Pool, a group of utilities covering 14 states, said the blackouts were “a last resort to preserve the reliability of the electric system as a whole.

The situation in Texas drew attention at Wednesday’s International Energy Forum, including messages of support from Saudi Arabia’s energy minister and OPEC Secretary General Mohammed Barkindo.

“As the extreme weather in Texas has shown, we cannot take energy security for granted, even in a country like the United States,” Barkindo said at the forum, which was held virtually.

Travel remains ill-advised in much of the United States, with roadways treacherous and thousands of flights canceled. Many school systems delayed or canceled face-to-face classes.

But even staying home can be hazardous in places without power.

Authorities said a fire that killed three young children and their grandmother in the Houston area likely spread from the fireplace they were using to keep warm. In Oregon, authorities confirmed Tuesday that four people died in the Portland area of carbon monoxide poisoning.

At least 13 children were treated for carbon monoxide poisoning at Cook Children’s Medical Center in Fort Worth and one parent died of the toxic fumes, hospital officials said.

In Texas, at least, temperatures were expected to rise above freezing by the weekend.

“There is some hope on the horizon,” Oravec said.

The weather also caused major disruptions to water systems in the Texas cities of Houston, Fort Worth, Galveston, Corpus Christi and in Memphis, Tennessee, and Shreveport, Louisiana. In Houston, residents were told to boil their water — if they had power to do so — because of a major drop in water pressure linked to the weather.

In Abilene, Texas, firefighters were hampered by low water pressure as they tried to extinguish a house fire this week.

“They had to watch that house burn,” City Manager Robert Hanna said Tuesday at a news conference.

Stories of kindness emerged from the crisis.

In Clinton, Mississippi, Army veteran Evelyn Fletcher has been cooking and delivering meals to sidelined truck drivers, travelers and people staying at hotels after losing power at home.

“They’re stranded, they’re isolated — people are in need of support right now,” Fletcher said.

On Monday, Fletcher made 85 meals. On Tuesday, she made 30 plates, while a local restaurant, T’Beaux’s Crawfish and Catering, cooked 75 plates of shrimp and gumbo that she and other volunteers delivered. And on Wednesday, Fletcher was cooking a pot of turkey noodle soup, hoping to deliver another 70 meals.

“People are worried about more snow,” she said. “We are going to keep people fed and keep them feeling hopeful.”

NewsNation affiliates from around the U.S. contributed to this report. The Associated Press contributed to this report.