It is SO dry here that I haven't been faced with this problem.
However, I do wear the SPD sandals that Blackberry uses. And, even in Colorado, I wear them winter and summer. I think they are GREAT, and you could put a waterproof sock on, or simply get your feet wet since your temps are so warm. Just like taking a bath.
Have an extra pair of socks, and when the rain stops put them on. The sandals are non-absorbent and dry quickly.