PMDs are the West's classic summer mayfly. They emerge from late June through early September on tailwaters and freestone streams that hold cool, oxygenated water. The hatch typically peaks between 10 AM and 2 PM, when water temperatures are climbing.
The naturals run #14–#18, with a creamy yellow body and pale wings that look almost smoky-gray when fresh. Match with a Sparkle Dun, Comparadun, or Parachute PMD. Trout key on emergers in the surface film as much as on duns — keep an emerger in the box.