Steaming Oven

"Yes this is steam rising out of the mud oven dome. It rained the previous 2 days and while the mud oven was still firm it had soaked up a lot of water and took a couple of hours of heat to burn it off." handyprojects.blogspot.com/feeds/posts/default
I don't really know how long an oven can last if it gets rained on a lot, but I'm sure a covering would definitely prolong the life of an earth oven.