We were there 1/11-1/15. It was chilly. My kids needed hats, coats & gloves for pre-park ADRs & waiting to get into the parks. We wore long sleeves & pants every day in the parks (gloves in the morning) but our last day when we wore short sleeves for a few hours in the afternoon (mid-high 60s). We swam one day & it was about 58 degrees. My 5yr old didn't care but it was pretty chilly for DH & me!
1/15 we were supposed to fly out & there was a downpour in the morning. It seemed to clear up by time we left for the airport (our flight was delayed 13-14hrs so we ended up leaving 1/16 instead).
I'm not sure about crowds. I hadn't been to WDW in 18yrs. It was certainly more crowded than 18yrs ago. We definitely kept running into the same people over & over again. Some times it would feel very congested & other times it was more open. We didn't feel overly crowded & wait times seemed manageable - our longest wait was talking Mickey about 35min at 6:45/7pm. Otherwise we didn't wait longer than 15-20min. We only visited 2 days MK & 1 day DHS.