Honestly, the temperatures in late January are so unpredictable, it's hard to say. My advice is to keep an eye on the weather and wait to pack until as late as possible, and even then, pack for all eventualities. I was at WDW in January this year and we had some days that were really nice (highs in the upper 60s, low 70s) but some days that were miserable to me, a Florida-born and Georgia-raised girl (highs in the low 40s with misty rain). At the very least, bring a light jacket that you can wear in the mornings and then take off as it gets warmer out. As far as rain, it's not as often or as predictable as the daily summer showers. On our last January trip, it misted for a few hours one day (it wasn't really heavy enough to call it rain).
