Quick answer: May is runoff season in Missoula. Snowmelt usually hits full bore by about the tenth of the month, and the main rivers run high and off color for a few weeks. The fishing does not stop. It moves. Plenty of Mays, one of the main rivers holds clear, fishable water and we are on it. When the whole valley is muddy, we fish the Clearwater River, the Missouri, or one of the quality lakes within an hour of Missoula. Dry fly chances are rare, nymphs and streamers do the work, and a guide who knows where the clear water is makes all the difference.

May is the one month people worry about, and they should not. Here is what runoff actually means, where we fish, and what a May day looks like.

What is runoff, and when does it hit?

Every winter the mountains around Missoula stack up snow. In late April it starts to melt, and by around May 10 the rivers are usually running at their highest and dirtiest. The Bitterroot, Rock Creek, and the Blackfoot all send their snowmelt into the Clark Fork, which makes the Clark Fork the last river to color up and the last to clear. High water also carries downed trees and logs, which is why floating the big rivers at peak runoff is a bad idea and why your guide will not do it.

How long it lasts depends on the snowpack. A light snow year can clear by late May. A heavy one pushes into early June. That is why May trips depend on conditions more than any other month, and why we would rather tell you what the water is doing the week before your dates than promise a river months ahead.

Where do we fish in May?

This is the part that surprises people. May is all about reading conditions, and there are three answers:

• A main river that is clear. Plenty of years, and plenty of weeks within May, one of the main rivers holds clear, fishable water while the others run high. Rock Creek clears faster than the bigger rivers because of its gradient, and the Clark Fork can hold a fishable window before its tributaries fully blow it out. When that happens we are right there on the Bitterroot, the Blackfoot, or the Clark Fork.
• Clear water somewhere else. When the whole valley is pushing muddy snowmelt, we go find clear water. Depending on the year that might be the Clearwater River, or the Missouri near Craig, a tailwater that barely notices runoff.
• The lakes. There are several quality trout lakes within an hour or so of Missoula, and May is when they shine: hungry trout, calm water, and no snowmelt in sight. A lot of visitors have never fished stillwater for trout, and it is a genuinely fun day.

The one constant: there is always good water to fish within a few hours of Missoula in May. Finding it is the whole game, and it is the game your guide plays every week.

What is the fishing like when the water is up?

When a river is high and off color, the fish pull into the soft edges, the back eddies, and the current breaks where they can rest and still grab a meal. Heavy nymphs that get down fast are the ticket, and streamers move fish that want a bigger bite. Your guide will work good water more than once, because in brown water the fish need a couple of chances to find the fly.

Dries are rare, with one exception. The Mother’s Day caddis hatch peaks around the middle of May and runs about three weeks, and it can bring fish up on any river that happens to be clear. The tributaries, which open the third Saturday of May, often give a better shot at it than the main stems.

What is a May day like?

Warming but unsettled. You might get a sunny 70-degree afternoon or a cold rain, sometimes in the same day, so pack layers and rain gear. Starts are relaxed. There are fewer anglers than at any point in summer. And there is a bit of an adventure to it, because a May trip goes where the fishing is best rather than to one set river. Come with an open mind about the water and you will probably be pleasantly surprised.

Why fish May with a guide?

May is the month where local knowledge matters most. Knowing which river is in shape, when a lake is turning on, how the runoff is timing out this particular year, and how to read high water safely takes years on these waters. A visitor trying to sort it out alone in May would likely have a long day. With a guide who is already dialed in to where the fishing is good, May can be quiet, productive, and a lot of fun.

Common questions about May in Missoula

Should I just avoid May? Not if it is when you can come. Call us. We will tell you honestly what the water is doing and set you up for a good day, even if the day looks different from the summer float you pictured.

Can you float the rivers in May? Sometimes, on a river that is clear, early or late in the month. At peak runoff, no. That is when we fish the lakes or drive to clear water.

Is the Missouri part of a May trip? It can be, by request, a couple of hours from Missoula. It is a famous tailwater and one of the options when the local rivers are blown out.

When does runoff end? Usually late May into early June, depending on the snowpack. By mid-June the salmonflies are on and peak season has begun.

What should I wear? Layers and a rain jacket. Waders are welcome on cold days, and we can lend you a pair if you do not own one, or you can rent from Rent Waders (rentwaders.com), a Missoula company that delivers to our shop. See What to Wear.

Book your May trip: (406) 728-4308