The meringue powder will stabilize the icing. If you are using 1/2 Cup shortening & 1/2 cup butter, try using the meringue powder and 3/4 cup shortening and 1/4 cup butter. It will hold better in the humidity. I have central A/C too and I still need to make adjustments in the hot humid weather. Good luck. It is the butter in the icing that is melting first. So use less until the weather cools down. That is what I do.
6/23/13 at 2:36pm