Baetis mayflies feature olive-gray to olive-brown bodies and medium gray wings. They often appear dark gray on the water. They're rather small, #1620, but they hatch in big numbers for long seasonal durations when few other hatches are on the water.

Baetis hatch from about noon to late afternoon or early evening in spring. This is the warmest time of day then. Despite that, they prefer overcast, humid conditions to hatch in. Cloudy, rainy, even snowy days bring out the best hatches.

This is a hatch you can depend on. Foul weather doesn't lessen it a bit; in fact, these are just the days you want to be on the river, looking for good hatches and rising fish!

All Season Long

Baetis mayflies begin hatching as early as March on some lower-elevation rivers and spring creeks. I've heard of some hatching even earlier than that. Where I live in Montana, Baetis show up about the third week of April on most rivers.

They'll hatch predictably from then into June. This gives about two months of rising-fish potential on spring and early-summer afternoons before waters rise too high, making possible a leisurely approach to some of the season's best dry-fly fishing!

An afternoon session on the river, a thermos of hot coffee, a dependable hatch, and numerous rising fish  what could be better? When an overcast, drizzly day is forecast in late spring, it's time to close up shop and head for the stream!

In the first part of the spring, midges will be the only other major hatch, with the addition of little winter and spring stoneflies on swifter rivers. Midges prefer humid conditions to hatch in, too, but care less about sunshine than Baetis do. Spring Baetis don't like bright, sunny, and arid spring days. Some will hatch, but not nearly as many as on cloudy, damp afternoons.