I don't know if this will help or not. I've had this problem in E. Washington at times. I usually have to run my filtered water through passive solar panels (black plastic tubes heated by the sun) to warm the pool to acceptable temps for the grandkids. If we get too much hot weather and the heating is not shut off, the pool gets too warm (got over 100F one time). What I did to cool the pool down was to run the water thru the solar panels at night after the air and ground temp was low enough to cool rather than warm the pool. I know that it stays pretty warm in Pheonix pretty late, but maybe running it from 10 pm until 8 am might help you as it has occasionallly helped me.