I live in Arizona so it's pretty easy to get into the 80's and with the weather coming up in the next week, I'll be lucky if I can keep the pool below 90 even running the solar heaters at night to cool it.
I let my pool temps run wherever the sun takes it. When it's hot here, 100-107, the pool warms up pretty quick but some nights we get a breeze and it will cool off with air temps into the 60s at night and then the pool cools down. It typically runs in the low to mid 80s. If it gets too hot, I add some fill water to cool it down and top it off as we can get a lot of evaporation pretty quickly. I had a cover for a couple years but it spent more time on the deck and it was a pain to mange. When it became old and brittle, it was recycled and not replaced. It also made the pool too hot.
I live in Eastern Canada, where the temperatures are currently 57 at night and 72 in the day. I keep the pool at 78 until the weather warms up. This might seem cool to those in the south, but you get used to it, particularly with the cost of propane (no natural gas) here! When the pool water gets to 84 in mid-summer, I leave the solar cover off at night to let it cool down, as we find the water too warm to be refreshing! Our "perfect" water temperature is 81.
86 to 88 are the best temperatures to have in order for the water to ease the pain I have of fibromyalgia - it's soothing without being too warm - love it! I can stay in the pool forever at those temps!
I have a spa, which i heat upto about 98 degrees cause a lot of little kids, don't want them to get too hot. keep the pool at 84 degrees, problem is people complain the pool is too cold "your pool is too cold to swim" lol cause they go in the spa first.
Our is at around 88ºF because my wife uses it for exercise therapy (with some swimming) and she's in for up to an hour and a half each day. I like it warm like that as well, but people who swim a lot would find it too warm.
84-86 seems to be our ideal temp. 84 for water aerobics and swimming, 86 for just hanging out in the water. If it gets over 88, some one toss me a bar of soap...I feel like I'm in a warm bath. Much less that 84 feels frigid in contrast ot our air temps which are over 100 much of the summer. The solar system seems to allow daytime heating or nighttime cooling as needed to stay pretty close to ideal.