After a snowy few days, Mainers should prepare for a subzero weekend that the National Weather Service predicts will deliver the coldest air and windchill temperatures of the winter.

January is almost always Maine’s coldest month, but this weekend will be particularly grueling due to its duration and dangerous wind chills that could create hazardous conditions across the entire state, according to Jon Palmer, a weather service meteorologist in Gray.

“The cold air at the North Pole is usually contained within a polar vortex,” Palmer said. “When that vortex weakens, a lot of that incredibly cold air spills out into mid-latitude locations. That’s basically what is happening this weekend.”

The “leak” was likely triggered by rapid winter temperature spikes in the upper atmosphere that weakened the wind barrier that keeps the cold air in place over the North Pole, Palmer said. The frigid air is now “gyrating” its way toward New England, he said.

On Saturday morning, Portland will wake up to an air temperature of 1 below zero, with a wind chill from a 10 to 15 mile per hour breeze making it feel like 14 below zero. Mountain towns like Rangeley will wake to air temperatures of 13 below and windchills of up to 40 below.

The air temperature will dip to 2 below in Portland and 17 below in Rangeley on Saturday night.

“The thing I’m particularly concerned about is how long this is going to last,” Palmer said. “Typically, the most dangerous wind chills are just in the morning. That’s not really going to happen this time.”

In the western mountains, wind chills are forecast to remain as low as 28 below zero through Saturday afternoon, Palmer said, maintaining a high risk for frostbite and hypothermia for anyone outdoors. In Portland, Saturday afternoon will feel like it’s 3 or 4 below zero, he said.

Despite the bone-chilling forecast, this weekend is unlikely to break a historical record. The record low for Jan. 20, for example, was set in 1971 at 21 below zero. To date, the average January temperature has been warmer than usual, clocking in at 26.9 degrees compared to the normal 23.4.

“This will be a good weekend to balance that out and come back to normal,” Palmer said.

Palmer expects the frigid temperatures to persist through the end of the month.

The Maine Emergency Management Agency is urging Mainers to avoid prolonged outdoor activities, dress in layers to prevent frostbite, not leave pets outside, check on elderly or sick neighbors, and provide shelter and drinking water for livestock.

Other advice: Follow manufacturer guidelines if using an alternate heat source and equip vehicles with blankets, a first aid kit, snacks and water, a cellphone charger, and a flashlight with fresh batteries. Residents should also check smoke alarms and carbon monoxide detectors.

People can visit MEMA’s website to find a list of warming centers operated by local towns or cities and local organizations. Warming center info is also available by dialing 211 (or 866-811-5695) or texting your zip code to 898-211 for a list of locations.