Is there a way to know if i'll need to heat or cool my pool?

[ahreno]

Looking at an L shaped pool, lets say 18x40x30, 8 ft deep, vinyl in ground.

I'm in norcal so lots of sun. summers are a lot of 95-100+ days, but the nights pretty much always drop to mid 50s to low 60s.

I'm less worried about heating than i am cooling. is there anyway to know what to expect the pool temp to do?

 

[proavia]

On hot days the pool temp will increase.
On cool nights the pool temp will decrease.

If you want to retain the heat, cover the pool with a solar cover - especially over night.
With 50-60 degree nights, the pool should cool off some without a cover.