Re: Can this fly line be used in cold water for steelhead?
One of the things that tends to happen with warm water or tropic lines in cold water is that they turn into a Slinky--- like the child’s spring toy with stiff coils that retain their shape and make it very difficult to shoot line through the guides.
Fly lines designed for cold water remain supple in cold water, but on the flip side their coatings tend to get “gummy” and they soften in “tropics” and high air/water temps.
I don’t have any experience with your Orvis line, but what you might try is putting it in the freezer for a while--- you could probably just put the whole reel in too to do it, but I think I’d strip the fly line off the reel and put it in a plastic bag just to keep it all together in coils (Ideally on an old fly line spool to replicate the tight coils of a line around the diameter of your reel spool), but leave the fly line still attached to the backing---- and just put the reel on top of the fridge (the door to the freezer should still easily close and seal over the backing). Leave it in there for an hour or two and see how springy the line is—you might want to string it up and try casting with it.
Even if it is a little springy with the freezer test, it might be fine for steelheading in Sept--Oct temps, but might become more of an issue when you're out there trying to clear the ice out of your guides in Feb March, so as Ard says, don't let it stop you if that's the only line you have, and just get a coldwater line if it starts to misbehave as temps drop.
And let us know how it performs if you use it for steel. Good luck!