Fished Hells Canyon about two weekends ago and ended up wussing out due to the bad weather.
The conditions are brutal! Driving down there is a hairy task, and keeping the ice off your guides and hands makes the fishing difficult. I noticed the temperature gauge averaged 13 degrees Farenheit around 11:00am. The wind also plays a crucial role in the locations' brutality, so If your a polar bear and don't mind getting numb hands, drift fishing off the banks can produce fair results.
I only fished for about an hour and a half, but during that time period I found that the steelhead are biting, as long as you don't mind the harsh conditions.
If anyone fishes down there this weekend, please reply and let me know how you did.