Extreme cold warnings are in effect in all three Maritime provinces, cautioning that the coldest air of the season is about to arrive in the region.

Extreme cold warnings are in place for New Brunswick. Wind-chill values making it feel like -35C to -45C are expected to develop Friday afternoon and last at least into Saturday morning.
There is an increased risk of frostbite with the expected wind chill. Environment Canada notes that, “frostbite can develop within minutes on exposed skin” and that “outdoor workers should take regularly scheduled breaks to warm up.”
More on what wind chill is, and the health hazards it poses, is available here.

Extreme cold warnings are also in effect for Prince Edward Island and Nova Scotia, with Arctic air set to move in. This is the first time since 2015 that extreme cold warnings have been issued for Nova Scotia and P.E.I.
For both provinces, wind-chill values of -35C to -42C are forecast for Friday night into Saturday morning. Residents are advised to continue to monitor issued weather alerts and check on their forecast.
The frigid conditions are a result of a combination of wave of Arctic air breaking off the polar vortex -- a semi-permanent circulation of cold air typically positioned over the Arctic -- and the presence of a strong storm off the coast of Labrador.
The storm will create a pressure gradient across the Maritimes that will drive a northwest wind with gusts of 50 km/h to 80 km/h Friday night into Saturday afternoon, with wind diminishing Saturday night into Sunday morning.

A returning southerly wind is expected, along with a mix of snow and rain for the Maritimes Sunday into Monday. That will result in temperatures moderating significantly during that time. In general, that means Friday afternoon and evening into Sunday morning will be the the coldest period forecast for the region.