The weather is definitely warm enough, what isn't is the water! It is probably only in a couple of weeks at best and although the warm days heat it, the colder nights lose it. This is why the July & August pools feel like a lukewarm bath, the heat has been taken in and as it doesn't cool down much at night, the heat stays in the water.
Once you are in it is fine, but it will be cold at first in May - especially if the pool was filled using underground well water, which is icy cold going in