We cruised in December, never had a problem keeping the cabin at a comfortable temperature (except if we left the verandah door open too long).
Public areas were comfortable, I say that because DW is always cold, and even she was comfortable. She is well known at her work for sitting outside on a 100 degree day at lunch time, in a sweater, having a hot cup of soup, so she really reallly really is cool most of the time.