Can two skilled flyfisher catch fish in 27F water?

A lesson in temperature.

John and Brad - Before Picture

It seem like a good plan. Rather than 2 hours risking life and traffic jams on I-70, we'd drive 1 hour to Waterton Canyon and walk in an hour on a dirt road to fish the South Platte near Littleton rather than the Blue River near Silverthorne. Air temperature was predicted to go from 45F to 67F so we could leave the fleece in the car on the walk in. Flow was 120 cfs.

About a mile in some Rocky Mountain big horn sheep joined us. The shelf ice had disappeared but the water temperature was only 27F and there was no sign of trout activity or hatches.  We walked past the Marston Diversion where Denver Water sucks from the South Platte. Above the dam water temperature rose to 32F but still no sign of any fish. This area above the dam according to fishing reports held many more fish. Not for us. By 1:30PM we'd had it and started the trek out. Once below the dam the whole flock joined us, the air temp was now 67F and the water temperature a surprising 42F. 

We could now see fish all over the place. Other fly anglers were having a great time and soon both Brad and I had landed half a dozen on an egg pattern. 

We both knew not to expect anything at water temperatures below 42F but you have fish the water you're wading. We never expected the water temperature to rise 15 degrees in 4 hours as the air temperature rose 22 degrees, but of course we're happy it did.