I just finished reading John McMillan's article as well, pretty interesting and much of it is pretty intuitive, except the part about his success on dry lines vs. sinks tips when the water is in the mid to high 30's (better success on dry line). I wouldn't have believed it had I not witnessed it myself. I've hooked chrome bright fish on the John Day in January on a floater with 33 deg. temps and ice floating downstream.
It would have been interesting in the article if John had mentioned how many wild vs. hatchery fish he hooked over those 8 years of testing and broken this down into dry line vs. sink-tip. I was hoping his email address would have been included in the article so I could ask him this question.
same thing is mentioned in Trey Combs' work, big BC steelhead busting dries with ice floating by.
I bet the race of steel has a lot to do with it, and the relative changes in temp as opposed to just what the temp is.
Of course, we're talking about wild fish behaving as wild fish do, in a relatively undisturbed environment too. Hatchery clones aren't known for being wild about dries in my parts or in his, the Washougal watershed. But I'm pretty sure McMillan said something like that too, didn't he?
Anecdotally I've seen John Hicks hook up 5 times in a day with the water temp just at 38F... I myself have done well that low too, but those were on OP rivers with no pressure and midweek. In general for winter fish on the coast I'm more worried about the right flows and proper clarity rather than temps.
Granted, I know solid scientific and anecdotal fishing evidence that temps affect the agressiveness of fish as temps near 50F, but in general we don't have control over it, so we just fish. I guess that's why we temper our expectations of a good day of fishing in the winter to be a solid hookup, and bringing multiple fish to hand in a day a spectacular outing.
Finally I do remember a snowy day on the Sol Duc where we witnessed a steelhead slurping BWO's off the surface in some soft water. At first we though it was a sea run cut, but it eventually did a head to tail rise and we started throwing our gear at it in earnest. This was when I fished gear, so after a couple of casts, we ended up landing a nice wild fish around 9lbs.
Just to give this a Midwest perspective, The other day I rose a steelhead on a swung fly, hooked it, and landed it in 33 degree water with shelf ice. The fly was only under the surface about 2". A guy I met on the river watched the whole thing. He was walking along when he observed the steelhead rise like a ghost, follow my fly, and eat it. The air temp was around 36 degrees. I was using a floating line with an intermediate polyleader and an unweighted fly. Friends of mine have caught steelhead on muddlers when the temperature of the water was at 32 degrees. It is not that we know what we are doing over here, but it is all we have, and instead of sitting inside, we venture out to swing two-handed rods in half-frozen water, and sometimes the fish cooperate.
Have confidence in the swung fly.
for some reason, catching a steelhead on an ass-freezing winter day really makes it for me.
I love summer run fishing too, don't get me wrong, but something about midwinter flyfishing for steelhead really seems to capture the essence of it.