The arctic air that has descended on Maine will be at its most frigid today, keeping highs in the single digits after a night of temperatures well below zero.

Forecasters said today’s highs will reach only 7 degrees on the coast and 5 degrees inland. Tonight’s lows are expected to hover around zero.

“This is the coldest air we’ve had in about two years,” said Michael Hill, a National Weather Service meteorologist in Caribou.

Emergency management agencies were urging residents to bundle up and heat their homes safely during the cold snap. Shelters were preparing for an increase in the number of people wanting to get out of the cold, and Maine officials waived restrictions on heating oil delivery.