Brrr. Wind Chill of 18 Below Possible Friday Morning

Ice dams are common all over JP, including this Prince Street home. Taken Wednesday, Feb. 11, 2015.

Chris Helms

Ice dams are common all over JP, including this Prince Street home. Taken Wednesday, Feb. 11, 2015.

The National Weather Service warns of dangerous cold in Jamaica Plain starting at 3 a.m. Friday. It issued an advisory to expect wind chills of -18 and temperatures of zero.

That’s cold even by our recent standards.

The advisory runs from 3-10 a.m. Friday.

The Jamaica Plain-based MSPCA reminds us that the cold can be dangerous for pets. So, among other tips, before starting your car Friday morning, rap on the hood to scare any cats that might’ve sheltered in your wheels wells or under your hood.

Saturday night is expected to bring a new type of hazard to hard-frozen JP: Rain. While a mix of snow and rain is expected, there could be as much as an inch of rain. That will add considerable weight to roofs already under pressure from snow and ice.

If your home, as many do, has ice dams, here’s one way to combat them. The rain could cause major damage as the ice prevents water from escaping your roof. It instead backs up under shingles and into your house.