That time of year it totally depends. You could have 80's or be pulling out the winter jacket. We have seen both conditions in early February. I would not buy tickets for a water park ahead of time, but I would leave some schedule flexibility in case it is warm enough.
FYI we went to BB one day in early Jan last year. It was the only day all week warm enough for it. The park was way understaffed for all the people (northerners on vacation) who showed up. So while the park was not crowded, there were long lines for food & lockers etc and they kept running out of food.