Generally, instructions given to pilots are to apply carburettor heat as required to keep CAT gauge needle out of the yellow arc. But notice how on many such gauges the arc stops short of the bottom of the gauge - this is deliberate because ice will not form on the butterfly in extremes of cold.
In the UK, it generally never gets that cold, but thats not to say elsewhere it won't. By adding heat in these circumstances you may well raise the temperature into the risk area of carburettor icing.
Follow the instructions in the POH, and if you fly a Robinson read Safety Notice 25