Paul Magom, a general contractor for PRM Builders Inc. in Salem, has seen icicles so thick they required a chainsaw to cut through them.
His company clears about eight to 12 residential roofs a day and a couple at commercial businesses.
He warned Wednesday that warmer weather can mean more trouble above.
"People have to worry about the underside melting and it gets heavier and more compact," Magom said. "It becomes a load issue."
Magom said his employees are harnessed on the roof; they gradually push the snow forward until it's off the roof.
"I do see homeowners doing it," he said, "but I think it's better to leave it to the professionals."
But the professionals are busy, very, very busy.
Stephen DeFrancesco, owner of DeFrancesco's Southern NH Quality Roofing in Londonderry, said he is seeing an unprecedented level of business. He said he is getting multiple calls a minute, from property owners concerned about their roofs.
"In the next two weeks, I expect a lot of homeowners calling who are watching ice dams melt and get into their ceilings and what not," DeFrancesco said.
Firefighters, too, are getting lots of calls.
Residents see water leaking down their walls or from their ceilings and panic.
"I think we will get more calls related to water damage," Londonderry Battalion fire Chief Kevin Zins said. "It's been so cold recently, the ice dams are staying frozen. We haven't had warm weather to allow that to melt. We expect more water problem calls."
Some of those calls are from residents concerned about the noise — creaks, moans, thuds — their home is making.
Those calls are likely less pressing than the ones from people with water pouring through light fixtures.
"They worry about the roof coming in," Pelham fire Lt. Robert Horn said.
He said it's more than likely the creaking, which can be as loud as a thud, is the result of a home contracting and expanding in reaction to the extremely cold weather.
Salem resident Michael Metcalf said he's tried to stay ahead of the trouble, clearing snow from his roof twice already this winter.
But Wednesday, the Lawrence Road resident has another worry — icicles.
"This is terrible," Metcalf said. "If something like this falls on you ..."
Earlier this week, State Fire Marshal J. William Degnan warned state residents to get that snow and ice off the roof — and to maintain a "fall zone" for the heavy stuff coming off.
Degnan cautioned residents to keep exits cleared and to be careful around fuel and gas lines.
There has been damage to roofs around the state, some of it substantial, he said.