I think they would show signs of heat stroke,floppy leaves, root rot and maybe leaf odemia(swollen sack in the leaf filled with water) .also the leaves would get dehydrated because they would have used up the water in them to try to keep cool, and because of the quick evaporation because of the excess heat they would be droopy. I have had it happen with African violets. Velleta

I think the heat would stress the plant and weaken the immune system so the symptoms can show up as just about anything. Cloud forest plants seem to be more fragile and would show leaf damage quickly while other plants might not show damage but might not flower because of too much heat. As usual the answer is " it depends ".