It hasn't been as bad here in Michigan, maybe high 80's/low 90's lately. But it's not cooling down much at night...maybe mid 70's is all. Since I originally brought this idea up of "cooling off" my tub, I've set it at 90 degrees, and left it hoping to drop the temp some. I left the cover off most of the day today because it was cloudy and only in the high 70's, and I've managed to bring it down to 93. Apparently my tub (Jacuzzi) is well insulated
We soaked the other night, and it was good, but still not quite cool enough for my experiment. Going to try to get it around 90 and do a soak and see what we think. In any case, I was planning a complete water change next weekend anyway, so that will be an opportune time to set the temp lower and try it out.