Welcome, blitz! A few questions come to mind so we can give you a good answer. First, is your substrate porous like wood or non-porus like ceramic or glass? Frankly, I don't know of anything that will work on wood to keep it from absorbing moisture and popping the tesserae off. If you're using something non-porous (a glass tabletop for example), I don't think you would have to waterproof it. Applying an outdoor sealer would probably work in your climate....I'm in North TX and ours is pretty similar. Most of the time I use thinset for both an adhesive and grout on outdoor objects. That way I can seal it and let it go. ;)

HTH,
Pat

If your table is a wood mosaiced pc, I'd bring it in in the winter and rain as it will start to swell. I use outdoor grout sealer I buy from a tile store. I don't buy it at like a Box store(Home Depot) cuz they only sell indoor sealer(bathrooms and such) so I go see the professionals. I've also started using outdoor grout as well, but none of my indoor grouted stuff is doing badly outdoors.

Thanks for the help! Im going to use a glass tabletop. My main concern was that the elements would get the best of the grout. I'll be sure to find some outdoor sealer. The creativity comes easy to me, its the logistics that cause me trouble. Its good to see a forum with so many truly knowlegable artists for guidance!

I found an outdoor penetrating sealer at Lowes and that is what I use. It was in the same aisle as the grout. There were 3 or 4 different kinds based on years of warranty, gloss, that sort of thing. I bought a matte sealer that had a 10 year warranty, I think....it was right in the middle as far as price goes. I'm sorry I can't think of the name of it right now. I mainly bought it help prevent the grout from getting stained and I used it on my terra cotta birdbath with no problems.