I'm not sure if you are familiar with a grower who used to post here, Kangativa. He grew some of the biggest sativa's I've seen in a very hot climate. I am quite familiar with the area he grew in and there are frequent days over 35C in that area. It is not a tropical climate but still very hot, almost sub tropical. Go a couple of thousand kms further North in the tropics and I have seen some very big plant pics (Wal's Laos for example).The tropics are definitely place specific and there are many micro-climates. I also posted a chart on this thread or elsewhere regarding how there are veritable subtropical zones within tropical zones, like Puerto Rico, where the climate is much cooler relative to other places like the ones you speak of. Colombia and Mexico, depending on the altitude or the valleys, might be hotter or much much cooler than Puerto Rico, for example. I think they are happiest in places where it rains, regardless of temps, although anything above 35 sure brings stress if it is constant throughout the summer and thus even if the plants thrive, they produce much less.
Where I first grew we got frequent days of over 40C, record was 45C. Plants absolutely thrived provided you kept up the water.