Yeah, forgot about the monsoons. They've been impressive the last few years. My trip was dry, week before and after not. Next item is the road. Sand Wash road is the the wash bed for the last mile or so. Condition depends and can vary day-to-day. Usually BLM blades it after a bad storm, but there can be a delay. I was glad I had a 4wd tundra, but some kid made it in driving a ford focus. When they say you should have good tires, they really mean it. Price BLM can be spotty on road knowldege, but Melannie at RRT in Vernal will know pretty much up to the minute.
I followed her advice and changed my schedule from 5 days to 6 and was glad I did. This year I am going in Oct. to avoid the heat, and planning for 7 days. Mosquitos should be gone, but I'm not sure the black flies ever are. I got bit just about every time I was busy getting set up for a rapid.