Frosting for outdoor wedding in July

What type of frosting is best used in summer so that it will not melt, crack and slide (fall)?

~You definitely don't want to use a cream cheese frosting.

A buttercream frosting won't do well if you use a butter/shortening combination. You could do pure shortening and add butter flavor like this decorator icing recipe.

Another option is to use rolled fondant.

You can also use royal icing for decorations as they will hold up nicely.

Your cake still should be kept inside, in a shady spot or at least out of direct sunlight. Make sure the bride knows she should serve the cake soon and not let the cake sit too long.