i'm adding this post on my experience yesterday...
i played an outdoor gig (on ebg) in the shade on a stage next to the rio grande river. it was about 100 degrees fahrenheit, humid, and about 112 on the heat index. i brought a fan for me, but none for my amp...
i used my focus series 3 (one channel) into a 4 ohm 18" and a 4 ohm 2x8" crossed over at 150 hz. we played for 6 hours. there were no issues at all with the rig, no thermal shutdown, just lots of bass all day long. later, ron
I should clarify that my Focus also performs perfectly well in the shade. The one time I had a problem with thermal shutdown there was no choice but to place the amp in direct sunlight. After the shutdown I used my car's air conditioner to cool the amp. By that time the sun had changed position and shade was available onstage. I put the Focus in the shade and had no problems the rest of the gig.