...for photography...
For myself,it can't really be too cold-so long as the lens dosn't fog,the batteries don't die and my fingers don't fall off I'm good to go.Anything over say 85 F and I'm pretty much not shooting that day-not into sweating all over my equipment or constantly having to wipe my brow.Granted that means that during the hot,hot days of summer my time out is limited;day off needs to coincide with a nice day that's not super humid.Of course if I were living in an area that was pretty warm all year long I would have adapted long before now.I'd imagine though that someone doing portraits outside or street photography wouldn't want excessive amounts of heat and humidity either.Or maybe it's just me....