It can be hard to find reliable universal crowd calendars so what I've done in the past is to look at Disney crowd calendars and compare weeks. That will give you an excellent idea - other than when there are special events. We went the last week of January one year and it was the most quiet I've ever seen it. However, it was also record cold weather that year - and it was the winter before the first Harry Potter area opened up. (We were also at Disney that week and same thing - the least crowded we've ever seen it - even less than the beginning of September which is super low crowds). I am not aware of the dates for the Harry Potter weekend or how that will effect crowds. So - if the end of Jan/start of Feb is not the Harry Potter weekend, then that would likely be an excellent time to go. As for Feb, I looked up a specific week in Feb when I was considering taking my nephews that week. I was very surprised how high crowd calendars had that week. (My nephews have a week vacation in Feb and one in April. The April one was only moderate crowds, so that's the week we're going instead).