I am making a cake for my niece's birthday this weekend and its going to be outside. Of course after the mild weather we have been having this weekend is supposed to be in the mid 90's. I am using Cali4Dawn's buttercream recipe which is 1/2 butter and 1/2 shortening. Will it melt if its outside for let's say an hour or so? Should I add Meringue Powder or maybe more powdered sugar?

Thanks,
Cecilia

It's possible that it could melt. The meringue powder might help. Keeping it out of direct sunlight will also help.

If it got hot in TX as it got in Louisiana yesterday & today I wouldn't dare put a cake outside until right before it is needed. It is sooo hot!!! Good luck! I hope it didn't melt on you.

Victoria~ Is white powder just like meringue powder? Never heard of it.

I'd definitely keep it out of the direct sun.. try to set up the table in the shade where it may be a bit cooler ... it's been so hot here where I live, I'd be afraid the butter in the icing would melt...

Just wanted to add, remember to factor in the humidex when you are considering the temperature along with putting it in the shade.
Butter melts between 82.4 and 96.8
Shortening 98-110 F.
Hugs Squirrelly Cakes

Hhmn, moving to a cooler place, haha?
Well, I have heard like was suggested, that if you can get Stay-Ice or a similar product it helps. But I cannot get it here. So I don't know what it is like to work with.
Generally people go with all shortening icing or fondant.
Personally, I would go with either buttercream, keep the cake in a cooler until just before serving, and keep it out of the sun. Cooler isn't big enough? Double garbage bag the boxed cake and stick it in a plastic tub or container with ice below it, the cake boxed and bagged sitting on a cookie sheet or large cooling rack, another rack or sheet over it, followed by more ice on top. That way the ice won't leak into the cake and also will not weigh down and smash the cake box. I have done this with a few outdoor cakes.
Now here is a recipe from an old Wilton post, I have not tried it out though. But in a lot of warm climates, they do add flour to the icing to make it more stable in high humidity.
You might want to try a small test batch to see what you think.
Hugs Squirrelly
The Recipe
Hot Weather Icing:
1 and 1/2 cups shortening
1/4 cup dry Dream Whip
1/3 cup flour, sifted
2 lb bag confectioners' sugar, sifted
2/3 cup water or milk
4 tsp vanilla, or 2 tsp vanilla and 2 tsp other flavoring

Combine shortening and Dream Whip, mixing well on low speed. Add wet
and dry ingredients alternately, and mix. Do NOT over mix. Denser than
buttercream, and good for roses and other flowers. One batch is more than enough for a 2 layer 8" cake.

Is there anyway I can buy this stay ice on line because I need it I live half of block away of the sea and the heat is on here and dose it work with ithalian and swiss butter cream