Here are some ideas for flowers at events in the heat:
1. use tropical flowers - with their waxy surface, they hold up well in the heat. Think orchids, birds of paradise, ginger, protea. And though they are a bit more costly per stem, even just a few stems artistically arranged by your floral artist make a big impact.
2. if the event is outside, ice down the water - add ice cubes to the water just as you are putting the flowers out. They like a cool drink just as much as we do! And if their stems are cool, their flower heads hold up better.
3. if the event is outside, put them out last minute, and in the shade!
4. Cost effective flowers that hold up well are all flowers in the chrysanthemum family (think standard daisies, spider mums, etc - and even though they're called a daisy, gerberas don't care for the heat so much, and aren't in the same flower family) or talk to your floral artist about the flowers best suited for the style and heat of your event!