Steelhead101- By consistent, I'm talking within a couple of weeks. Certain things will trigger a few early fish to start trickling in for sure, but major runs are very consistent, and by paying close attention can be easily timed. Like I said, in the case of salmon, spring fed rivers with natural reproduction generally see an earlier push of fish. Many assume that when they see fish in August they are early, when in fact these rivers see those runs year after year.
When I first started steelheading I used to go by that same adage that early spring means early run and vise versa. I used to base my timing on water temps and flow, then I started paying closer attention to day length windows and once I realized how important of a factor this was in run timing my catch rate increased dramatically. Whether it's fall salmon, or spring steelhead, when I look back at my notes, my fishing success comes around the same time every year, no matter what the weather conditions. Flow and temps are obviously still factors but day length windows are the same every year, and generally so is the fishing (give or take a week or two).
Fall steelhead are a little different. They are months away from spawning, and water temps and flows play a much bigger role in run timing. Fall steelhead runs are less urgent and they can wait for the perfect conditions, or not run at all (I've seen it happen in years with very low water). I've seen fall runs begin as early as August, and as late as late December. For fall steelhead I tend to base my run timing on water conditions as opposed to day length windows, which can make it a lot less consistent than spring run steelhead.