Yes, i think you need to richen it up. Heavy cold air requires we adjust the carbs. Adjust your air screw richer and increase the idle. I believe you're using the TM32 and dont know what you have in there. Others on this forum put in larger needle and main jets for these colder months. Im still using the BS29 CV carb, but i've gone up to from a 117.5 to a 122.5 main, and turned the mixture screw nearly a full turn richer (i did this at around 50 degrees). The starting circuit depends on your air screw and pilot jet (seems that a 30 is just about right for your carb).
Batteries are also less efficient in the cold. You didnt say how your starting. If your using the ES, its critical for the sprag that you keep that voltage up, otherwise in a lean condition and low battery, the sprag will die.