It gets to 110 to 120 in the high summer here.
At night, I will wear a polo/t-shirt and shorts. Its that hot. If I'm going to a bar/club with a dress code, I'll wear a polo and jeans and be miserable or hope they keep it freezing inside.
For business wear, I wear the least amount of clothing that is still acceptable. In most cases, that means a dress shirt and wool pants. I don't find that tropical weight keeps me any cooler than 3 season weight wool. Wool is cooler than cotton I've found and keeps the crease & shape.
The lightest weight cotton shirt is the best for staying cool outside, although inside they usually keep it freezing so I always bring a jacket just in case. I'd love to have some of that twisted yarn stuff, but its out of my price range. Seersucker would probably be inappropriate and honestly in 110 degree weather, it doesn't matter what you wear.