Have been to KL and Langkawi twice at Xmas, the first trip to KL was sunshine all the way for 5 days with no rain at all and blue skies, last year we were there for 4 days over xmas and it rained most of the time, it was not that humid, we saw some spectacular thunderstorms. Langkawi again is changeable. First time had rain for a couple of days last Xmas it was pretty good although they had had loads of rain just before we arrived on 25th December. The New Year do the first time was completely ruined by the rain so last year they had it inside, not quite the same.