At my old home, on those really hot days I would turn the filter on, run the aerator(which sprays water into the air), and jump in the pool wearing a big straw hat. Kind of a non-mustachian waste of energy, but there are some days where you have to take extreme measures.
You can also get a shade umbrella and base for like $80 new or much less used. Also a good idea to mix the water up right when you get in, so the warm water at the top and cool water on the bottom mix together.