Ours stayed open all winter. We've kept it clean. Currently, the water is up to 75 degrees (location S. Arkansas.) Our 5 year old grandson officially opened it about a week ago when the temp was 72. His mom was worried about hypertermia, but she couldn't keep him out. He was fine. He was in and out, mostly in, and it was a hoot to watch him. I may try it at 78 or so, but last fall, I couldn't stand it below 82 degrees. There's a cool snap forecast, so we may drop a couple of degrees in the next few days.