The weather in Jan. should be great. We were there a few weeks ago. Weather was warm during day, but not too hot and humid. Very comfortable, and cooled down at night. If you want to enjoy dinner by the pool you will need a sweater or light jacket. We loved Amantaka, and highly recommend the khan pool suite which we had#7 with a large terrace and pool. Also highly recommend the afternoon trip down the Mekong, and the spa! The property was full as it was NYEve timeframe, but the service was still excellent.