At last, we have a thaw.

After spending most of the past few days in subzero temperatures, Minnesotans can finally unwrap the woolen scarves from their faces and move their fingers and toes again. The deep freeze that gripped the state sent dozens of people to hospitals with frostbite, closed schools, halted mail delivery, froze pipes and waterlines, stalled cars and shut down the heat for about 150 Xcel Energy customers near Princeton.

But even as temperatures push into the double digits on Friday and flirt with 40 degrees this weekend, the damage may linger.

On Thursday, plumbers were flooded with calls about frozen pipes. Rich Peterson, co-owner of Cities1 Plumbing and Heating, had three extra thawing machines shipped overnight from Pennsylvania.

“I’ve been in the industry now for 20 years, and this is probably the worst that I’ve seen it,” he said.

His company received about 68 calls for frozen pipes or heat problems on Wednesday, and 47 more by midday Thursday.

Mendota Heights resident Polly O’Brien, 95, discovered she had no hot water in her kitchen Thursday morning. After she thawed the pipe beneath her sink with a heater, water gushed out.

She was fortunate to snag a visit Thursday from Jason LaBelle with Rascher Plumbing and Heating.

“That was lucky,” O’Brien said as LaBelle got to work. “My neighbor had a couple of other [plumber suggestions] — they said, ‘Well, we can’t get there until Monday.’ ”

The freeze extended beyond indoor pipes to outdoor waterlines and septic systems, said Scott Ende of Ende Septic Services in Rogers.

“I have a bathroom off the outside wall of my house and even that water line froze on me,” Ende said. “So we’re seeing everything.”

Ende said well-designed and installed septic systems shouldn’t freeze, but some systems have design flaws. In other cases, people have packed down the snow atop a mound-based system.

“We get out there and you might see horses standing on top of the mound,” Ende said. “We’ve seen it where kids were using the mound as a snowmobile jump.”

Minneapolis received complaints about no heat or very low heat from tenants at 20 rental properties, most of them apartment buildings, including one with about 50 tenants.

The city’s landlords are required to heat buildings to at least 68 degrees this time of year. City staff leaned on the relevant landlords to make the fixes, most of which were completed.

“People absolutely should call 311 if they think that their heat is too low and report it,” said Kim Keller, the city’s interim director of regulatory services.

Heat back in Princeton

In Princeton, Minn., Xcel restored heat to customers who had been without since late Tuesday. That also meant it no longer needed its customers across the state to dial down their thermostats to at least 63 degrees in an effort to conserve fuel.

The outage likely was due to a loss of pipeline pressure, Xcel spokesman Matt Lindstrom said in an e-mailed statement, apologizing to affected customers and adding that Xcel engineers and planners are looking for ways to improve the system “so we can avoid situations like this in the future.”

When there is a surge in demand, more gas can be essentially flowing out of a utility’s distribution system than coming into it, creating a drop in pressure, said Richard Kuprewicz, president of Accufacts, a Seattle-based pipeline safety consultant. If the pressure gets too low, pilot lights can go out in homes and businesses, allowing gas to flow out, he said.

Gas distributors will curtail service to prevent that from happening, he said. “If you curtail gas and have to shelter people, that is a pretty serious and extremely unusual situation,” Kuprewicz said.

The Minnesota Office of Pipeline Safety, an arm of the state’s Public Safety Department, is investigating the situation.

Silver lining

The week of brutal cold delivered a bit of mercy for owners of parked vehicles in St. Paul who have risked being towed in the wake of the heavy snowfall at the week’s start that prompted a snow emergency.

Police spokesman Steve Linders said the department’s parking enforcement officers have shifted their focus “to calls for service and vehicles that are creating a safety hazard. Due to the cold weather, we are backing off towing vehicles that may be stranded because they won’t start.”

Minneapolis made a similar gesture on Wednesday.

Much warmer weather will arrive Friday, according to the National Weather Service in Chanhassen. The metro-area high will be 20, with Saturday’s high near 36 and Sunday’s 41.

But along with the mild temperatures will come some unpleasant stuff — patchy fog and drizzle on Sunday and rain, snow and sleet on Monday. By Tuesday, the Weather Service said, snow will return, and the high will be only 16.

The good news? That’s 16 degrees above zero.

Staff writers Mike Hughlett and Tim Harlow contributed to this report.