Kalist,
Minus (-) I don't know what that is !!
Gees, I complain when it gets below +65°F !!
Understood on the Warm Up'er, but, you don't have to get a real fancy Meter, to do basic checks.
Don't know if you have a Radio Shack type store up there, but a simple Analog Voltmeter that has Volts and Ohms Scale on it will do fine. (under $10us)
Now, at those temperatures, funny things happen to metal, it's possible all you need to do is thoroughly clean your Battery Terminals, and make sure they're tight.
The Meter will let you know if the Power is there, and then you can proceed to make sure it's making the trip to the Ign and Starter by tracing the Voltage with your Meter.
(Set the Meter to the 20 DC (volt) scale, and push the Points of the handles, DIRECTLY on the Battery Posts, not the Clamps that are on them. Red is Positive, Black is Negative. Should read about 12-14 Volts when it's not running)
Beyond this test, you can check how much Voltage you have in your house, find out if a Light Bulb is good or not, lots of things. Read the little Book, it will suggest stuff for you to do with it.
Let us know how that goes !
Have a good Day !
S.W.