Well, mold comes to mind. Are you speaking of dried tomatoes which may be done in a dehydrator or are you speaking of tomatoes actually dried in the sun?

Carol

They will dry just fine in the sun if the air is very dry.

Your outdoor drier needs to be screened to keep the bugs and flies off the food.

Best drier in the world is an old fashioned gas oven with a constantly on pilot light. I suspect that they don't even make those any more.

If your outside humidity isn't low, invest in a food drier.

Just speculation about your zone but I wouldn't think actual sun drying would be possible there without mold problems. But what you could do is a 1/2 sun drying and then freezing them. Just cut in halves or quarters (depending on the variety), gently squeeze out much of water, salt, and dry in the sun until about 1/2 way done. Then pack in bags and freeze them.

Dave