Hey, I'm about halfway through a bloom growing an outdoor Pre98 Bubba and I'm about to start blooming a outdoor Blue Dream hydro.
Attached is a pic of my pre-98 bubba from a few days ago. It's a little burned from a combo of foliar spray and too much sun/heat stress from my reflectors.
Anyways, I wrapped my res in foil tape, which really helps. If I see its starting to get really hot, I use frozen water bottles. I haven't had any temp problems so far and I'm in SoCal.
Also, do you have any lights on it at night? My Bubba is flowering from just being left outside 24/7, and I would say it is light out from about 7 am to 8 pm.