Thousands of frustrated Texans have shivered in homes without power for a second day after an icy winter storm across the southern US, as fading hopes of a quick fix have stirred grim memories of a deadly 2021 blackout.
The freeze has been blamed for at least 10 traffic deaths on slick roads this week in Texas, Arkansas and Oklahoma.
And even as Texas finally began thawing on Thursday, a new Arctic front from Canada was headed toward the northern US and threatening New England with potentially the coldest weather in decades.
Wind chills could dive below minus 45 degrees Celsius.
In Austin, city officials compared the damage from fallen trees and iced-over power lines to tornadoes as they came under mounting criticism for slow repairs and shifting time lines to restore power.
"We had hoped to make more progress today," Jackie Sargent, general manager of Austin Energy, said. "And that simply has not happened."
Across Texas, more than 280,000 customers were without power on Thursday night, down from 430,000 earlier in the day, according to PowerOutage.us.
The failures were most widespread in Austin, where impatience was rising among 150,000 customers nearly two days after the electricity first went out, leaving many also without heat.
Power failures have affected about 30 per cent of customers in the city of nearly 1 million at any given time since Wednesday.
By Thursday night, Austin officials backtracked on early estimates that power would be fully restored by Friday evening, saying the extent of the damage was worse than originally calculated and they could no longer predict when all the lights would come back on.
For many Texans, it was the second time in three years that a February freeze caused prolonged outages and uncertainty over when the lights would come back on.
Unlike the 2021 blackouts in Texas, when hundreds of people died after the state's grid was pushed to the brink of total failure because of a lack of generation, the outages in Austin this time were largely the result of frozen equipment and ice-burdened trees and limbs falling on power lines.
But the differences were little comfort to Austin residents and businesses that also lost power for days two years ago.
Among those still without power Thursday was the Central Texas Food Bank, according to Travis County Judge Andy Brown, the county's top elected official.
"They have 21 counties to serve. They've been down for at least three days now. There's a lot of need that they have," Judge Brown said.
School systems in the Dallas and Austin area, plus many in Oklahoma, Arkansas and Memphis, Tennessee, closed on Thursday as snow, sleet and freezing rain continued to push through.
In Austin, schools will not open until next week at the earliest.
Hundreds more flights were cancelled again in Texas, although not as many as in previous days.
Airport crews battled ice to keep runways open. By Thursday morning, airlines had cancelled more than 500 flights at Dallas-Fort Worth International Airport — more than a quarter of all flights scheduled for the day.
Still, that was down from about 1,300 cancellations on Wednesday and more than 1,000 on Tuesday, according to FlightAware.com.
Dozens more flights were cancelled at Dallas Love Field and Austin-Bergstrom International Airport.
Another wave of frigid weather in the US is on the horizon, with an Arctic cold front expected to move from Canada into the northern Plains and Upper Midwest and sweep into the north-east by Friday.
In a briefing on Thursday with the federal Weather Prediction Center, New Englanders were warned that wind chills — the combined effect of wind and cold air on exposed skin — "could be the coldest felt in decades".
The strong winds and cold air will create wind chills "rarely seen in northern and eastern Maine", according to an advisory from the National Weather Service office in Caribou, Maine.
Jay Broccolo, director of weather operations at an observatory on New Hampshire's Mount Washington — which for decades held the world record for the fastest wind gust — said on Thursday that wind speeds could top 160 kilometres per hour.
"We take safety really seriously in the higher summits," Mr Broccolo said, "and this weekend's forecast is looking pretty gnarly, even for our standards."