I would certainly bet that you are seeing higher velocities and higher pressures on warmer days -- and if the ammo is sitting in the sun for a good bit on a hot day (or left on the seat of a car...), I'd bet it would go even higher.
Hodgdon says that 40.2 grains is a max load for the Hornady A-Max (not the same bullet you used), but if you didn't see a whole bunch of high pressure indicators when you shot the load at 80 degrees, I wouldn't guess that it's a dangerous load...but every rifle is different.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.