[HT] firearms and cold

[Green-Neck]

Hello fellow enthusiasts.

I am writing an 1930's arctic rocketeers campaign at the moment and am wondering about the effect of cold on automatic weapons.

HT p.80 specifies '-1 or worse' to malf for hostile environments such as cold.
I would like to get some idea of how much penalty to apply to malf given different temperatures. I would like to create different penalties from say, 0 deg Celsius, to -25 degrees Celsius (-13 deg. F) with an appropriate wind chill factor for 120 mph winds (max rocket pack speed, -52 C, -61 F with wind chill).

Also it would make sense that the players could cycle their weapons to see if it has frozen - make an attack roll without firing to see if Malf occurs?

As I live in Australia I'm not too familiar with the cold and would appreciate some help!