Very good, sensible advice. I advise running down to Home Depot and picking up a proper hose nozzle while you still can. /sarcasm.
Actually, having survived St. Helens micro-eruption (compared to Yellowstone possibilities) and having been inconvenienced for a few weeks by it, I am in awe of volcanos and the possibility of substantial destruction. Here, in eastern Washington, I can just imagine no wheat or potato production for 2-3 years, and having all the irrigation reservoirs and canals jammed with ash. No irrigation => no production in this part of the country. If the ash is anything like St. Helens, it essentially turns to concrete after a few wet/dry cycles.