Part of maintaining a swimming pool, spa or hot tub includes preparing it for those months when you won’t be using it. Also referred to as “closing your pool,” or “pool closing,” the time to tackle this task varies, depending on the climate or region in which you live. Most experts believe that pools should be closed for the season when nighttime temperatures are in the 40s and daytime highs are in the mid 60s to low 70s. If you close it too soon, you risk the possibility ofalgae overgrowth. If you wait until trees really start to shed their leaves, obviously you’ve got a big mess to contend with.