The winter weather that has overwhelmed power grids unprepared for climate change 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.

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 parts of the Southern Plains, the National Weather Service said.

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.

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.

“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 weather has threatened to affect the nation’s coronavirus disease 2019 (Covid-19) vaccination effort. President Joe Biden’s administration said delays in vaccine shipments and deliveries were likely.

After visiting Milwaukee on Tuesday, Biden said the weather was as “cold as the devil up there.” SOVEREIGNPH

POWER OUTAGES

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

Blackouts lasting more than an hour had begun before dawn Tuesday in and around Oklahoma City, stopping electric-powered space heaters, furnaces and lights just as temperatures hovered around minus 8 degrees (minus 22 degrees Celsius). Oklahoma Gas & Electric urged users to set thermostats at 68 degrees Fahrenheit (20 degrees Celsius), avoid using major electric appliances and turn off lights or appliances not in use.

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.”

Travel remains ill-advised in much of the nation, with roadways treacherous and thousands of flights canceled. Some of the fatalities involve people dying in their cars in subfreezing temperatures. Many school systems have delayed or canceled face-to-face classes.