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.
Australian Slang: Meaning that your really thirsty, usually words heard around a pub when no drinks are being served because sevice is slow and the locals are getting impatient.
-Oi Shazza! Could you hurry it up a tad I'm dry as a dead dingos donger over 'ere
-Chuck us a coldie, all this hard yakka is making me as dry as a dead dingos donger!