I live in southern Missouri and I would open mine sooner except the Maple and Oak trees haven't dropped their seeds yet. If you have trees near your pool that drop seeds you will spend a lot of time keeping the pool clean. I opened early one year and a spring storm deposited a large amount of seeds pods from my neighbors LARGE pin oak and I spent hours cleaning the green stains from the water line around the perimeter of the pool. Just a word of caution!!