Hi

I am a fisher from Colombia S.A. so our fishing is a little different from yours up there (we have rain all year, it can range in a same day from light showers to monsoon-like storms then back to bright and sunny. The tropic!) but here is what I have found works best round here:

The best patterns are soft hackle wet flies, for us here, bright colors (red, yellow, green, etc. bodies, with light brown or white hackle) work best when rain is still falling while dark colors (black, dark grey or brown bodies with dark brown, black or grizzly hackle) and fat bodies work best just after the rain stops. If the pattern has a little peacock herl in the body it works GREAT. Sizes for us here range from 6-12 for soft hackles.

The approach that triggers the most strikes is casting up and across letting the fly dead drift and then slowly rising up the tip of the rod to make the fly swing across the stream and finishing with not too short but fast, jerky retrieves.

Just before rain, nymphs (hare's ears, pheasant tails or whatever works in your waters) work great retrieving with very short, fast pulls bringing the fly to the surface, no split shots or sinking lines, may be nymphs get crazy about emerging just before it rains, who knows?

The same flies work for lakes, better in bigger sizes but any size will do fine (we mostly fish lakes round here), for soft hackles and if there is wind try a floating line a long leader, 9ft or more, cast 45 degrees to the oposite side the wind is blowing, above active trouts (if seen, if not where ever you've got action before) and let the wind bend the line in a big curve, strikes may come any time while the fly moves dragged by the line.

If there is no wind look for any moving water (streams that feed the lake) and cast so that the fly drifts and swings; if raining, flies that are just below water surface work best.

Just before it rains nymphs work incredibly. Use whatever apporach you've used before, it WILL work.

Hope this helps.

Dave