I agree. My boat unfortunetely sits outside in my backyard,yearround,and at this moment is buried under a fresh blanket of snow. It is double tarped ,second tarp acting as a tent to keep snow weight off the towing tarp. We just went through a cold snap with temps including windchill hitting -39Celcious. Don't know the conversion for this. All i can say is this is @#$% cold even for us.

Getting back on track this is how i winterize my boat every year including taking batteries out and charge and store them in my basement ,furnace room,topping with a charger a couple times during winter.My primary battery is still good and it came from 07. This year i will serious look at replacing,but i have had it tested and they(battery shop) keep telling me its still fine.

You should be fine...