We are also in southern Ontario. The kids have been in the pool each day since Friday. Water was 79 yesterday, but it's cooling down now (77 today). We've had hot days for over a week, so the solar panels did their job well. The nights have been warm and humid, so the pool did not lose too much heat at night.
Wouldn't it be great if the pool did not lose any heat at night? I've not found a good way to keep all the heat the pool gains during the day. Even with a solar blanket, we lose from 2 to 4 degrees.
..Bill