Not sure about how cold it gets in New Hampshire but -40 is the norm for January over here on the western Great Lakes. At that point, even the sweetest coolant mix can start to get. Only cure for that is a block heater. Factories offered an in-block version that looks like a miniature edition of the heater element from a house hot water tank. Better is a circulating heater that is plumbed into one of the heater hoses or into the delivery side or lower rad hose.
Issue with the block heater is that it generates a localized area of warm coolant that doesn't move all that far from the element; no large scale circulation. If your vehicle is computerized then the water temp sensor sends readings to the CPU. What happens when you start up cold is that the coolant is cold at the sensor and that is the reading sent to the Processor which adjusts the warm up cycle accordingly. Then , all of a sudden, here comes that pool of warm coolant, The sensor reads that and sends the amended reading to the processor, but then that pool moves on and the sensor reading changes again. These abrupt changes confuse the processor so it throws the equivalent of a "WTF?" code up on the dash. That ends up having to be scanned and deleted. to reset the system.
That is why the circulating unit can be the better option. Because it not only warms up the coolant but encourages it to move through the coolant passages, all the coolant more or less acquires the same ambient temperature, which, on initial start, the coolant sensor reads and submits. No violent shifts in sensor data due to hot and cold variants, so no confusion in the binary based peanut brain of the processor, so no codes thrown.