Winter weather that has 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.

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 climate change 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.

Some power companies resorted to rolling blackouts (temporary service shut-offs) in areas to meet extreme demand for heat and electricity as record-low temperatures were reported in city after city.

Nearly 3 million customers remained without power early Wednesday in Texas, Louisiana and Mississippi, more than 200,000 more in four Appalachian states, and nearly that many in the Pacific Northwest, according to Poweroutage.us, which tracks utility outage reports.

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 Thursday. Winter storm watches were in effect from Baltimore, Maryland, to Boston, Massachusetts. 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.

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 people, the agency said.

Entergy imposed rolling blackouts Tuesday night in Arkansas, Louisiana, Mississippi and Southeast Texas “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 power company.

Travel warnings remain in much of the United States, with icy roadways and thousands of flights canceled. Many school systems delayed or canceled face-to-face classes.

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

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