How Pool Temperature Effects Pool Chemistry
It's probably not possible, or sensible, to try and define one ideal swimming pool temperature, as different swimmers will have their own individual preferences. It's better to think in ranges. In general most people will feel comfortable in water between 75 and 85°F.
When the temperature of cool water increases, whether by artificial heating or natural seasonal changes it will have an effect on the pool chemistry. The higher the pool water temperature, the more dissolved solids will build up. Some of these are the kind of contaminants that chlorine reacts with. Higher pool temperatures will also burn off your sanitizing agent more quickly. In addition algae have a tendency to grow faster in warmer water and it makes sense to be more diligent in keeping the pool free of any algal spores.
So be prepared in warmer temperatures to use more chlorine and other pool chemicals. Pool experts normally recommend at least a once weekly pool shock treatment in warmer temperatures. But if you are using your pool heavily you might want to shock the pool even more regularly than this. Remember also that higher water temperatures will mean higher water evaporation rates. So you'll need to be more aware of pool water levels and be quick to fill up your pool to keep the water in your skimmers.
It's a good idea to more frequently test your water chemistry during the warmer months or whenever the pool is being heated. In particular, keep your eye on total alkalinity levels. In warmer weather your total alkalinity levels should be lower than in cooler temperatures. Muriatic acid is a popular pool chemical used to lower alkalinity. Remember that you'll have to adjust your pool maintenance regime throughout the year whether or not you're heating the pool. Of course this is particularly the case in areas that have hot summers.