I live in New Orleans and I feel your pain. I use an Italian buttercream for outdoor receptions and it works out well for me. I've had cakes sit in the blazing heat for the lenght of the event with no problems. My recipe is as follows: Beat 10# butter to soft and light (the lighter the butter, the lighter your buttercream). Remove butter from bowl and set aside. Clean bowl thoroughly. Place 5 c. clean egg whites into your bowl, and start cooking 6# sugar. When the sugar reaches 112c, start whipping your whites. When the sugar reaches 115c, turn it off and add it to your whipping whites (italian meringue). Whip till cool, then slowly add your butter. You can add titanium oxide to it if you want it whiter. Good Luck.