the answer dry as... is a Texas oilfield from the time of the boom in East Texas. although it didn't happen much at first wildcatters would find that their well did not come in "That well was a dry as a popcorn fart" from the land where they call cokes soda.
Dry as the desert. Lacking all moisture. Usually used when describing an extremely hot day, or really overcooked food. Gives the same feeling as when particularly dry food gets caught in your throat.
Similar to overcooking a bag of microwave popcorn; it's a fart that smells so bad that there is no way you can hide it. It fills a room and never seems to go away.
May leave burn marks in your pants.
Quick honey, open a window, I just had a burnt popcorn fart rip through my shorts!