Not sure if you're serious, but I'm pretty sure it was quite a bit warmer last year during early-season practices, especially overnight. Temps in the 40s and 50s will cool a pool pretty quickly, especially if the air temps aren't getting at least well into the 70s with sun regularly.
The kids (we're talking 8&Us here) were miserable. Blue lips, teeth chattering, shivering. It's one thing if you're in the sun and able to warm up a touch, but these kids are in a pool that's almost completely shaded by 5:30 pm, with water temps that couldn't have been higher than 67 or so and air temps at about 72 with a breeze. It was just too much for them.
If we were talking 13-18s, then screw them - they can handle it!