I just made a batch of the same buttercream I always make with all the same ingredients and fresh bags of powdered sugar and for some reason it came out gritty. I've never had this happen before and can only assume it's because of the weather. It has been VERY hot today which is pretty unusual. I don't have ingredients or time to start again and I was wondering if anyone has any ideas to smooth it out. I've tried whipping it more, cooling it down a bit and whipping it more, adding more liquid, more powdered sugar and nothing is helping. I'm going to let it sit overnight and try beating it again but if anyone has any tips or fixes I would greatly appreciate it!
Try adding some cream or half and half instead of water, also make sure to keep your frosting covered, air will dry out the liquid and make it gritty.
Oh my, sounds like you tried everything I was going to suggest
How did it work out for you?