As we approach the end of July here in Southwest Montana, what we most feared this winter is coming true. The low snowpack from this winter and the hot weather over the past few weeks are making it challenging to fish in the ladder part of our 2024 summer. Warm water temperatures plague many of our trout streams in the Greater Yellowstone Region, and it doesn’t look like it will end anytime soon.
Snow is the lifeblood of the Rocky Mountain West. It keeps our rivers flowing with cold water and fuels the rest of the ecosystem through dry summers. With below-average snow this past winter, the region’s rivers flow at warmer-than-normal temperatures. The low flows and warm water are unsuitable for trout and anglers planning to fish over the next few weeks.
Why are warm water temperatures a problem in trout fishing?
Warm water temperatures and low stream flows cause harsh living conditions for trout. Trout require cold, highly oxygenated water as they are cold-blooded animals. In low-water years, water temperatures warm, and oxygen levels decrease. These conditions create a stressful environment for trout and can cause them to die if warm water temperatures precede for multiple days.
Regardless of fishing pressure, these harsh conditions make it hard for them to survive. Add the fishing pressure the streams see during July and August, and you have a perfect storm for fish mortality. While water temperatures are high, catching and releasing trout is not safe as there is a high probability of fish mortality.
What water temperatures are unsafe for catching and releasing trout?
Personally, I hesitate to fish in any water warmer than 65 degrees Fahrenheit. Catching and releasing at these temperatures becomes unsafe, and the fishing is often slow anyway. Rarely do I find good trout fishing at higher water temperatures, so I plan my days on cooler watersheds. Optimal water temperatures for most trout species are between 55 and 65 degrees Fahrenheit. Water temperatures above 70 degrees can cause fish kills if trout cannot find refuge in colder tributaries or deep pools.
Montana FWP and other agencies do their best to close fisheries to protect the trout as water temperatures warm. As I write this article, many fisheries in southwest Montana and Yellowstone National Park are closed or under hoot owl restrictions. Use these links to view the current restrictions.
What are hoot owl restrictions?
Hoot owl restrictions close a section of the river to fishing exclusively during the cool hours of the day, from 12 am to 2 pm. No fishing is allowed after 2 pm, which is often the warmest part of the day. Again, these fisheries not only have higher mortality rates when catching and releasing trout, but they don’t fish well this time of year anyway.
Here are a few fisheries I often avoid during late July and August due to slow fishing and warm water temperatures. These differ yearly, but this list may help you plan your late summer trout fishing in Montana.
The Lower Madison: This section of river is rarely worth fishing after July 1st and is often the first river to close in Southwest Montana.
The Big Hole River: The river gets very low during July and August, making fishing tough. I usually avoid it most of the summer.
The Jefferson River: This one may be the worst of them all. Do not plan on fishing the Jefferson during July and August.
The Lower Beaverhead and Ruby Rivers: These tailwaters stay cool below the dams but are often too warm to fish in the lower reaches until the fall.
The Lower Gallatin: I have been surprised by how warm the Gallatin gets in the valley over the last few years. I may keep this reach on my radar, but I always check water temperatures before fishing this time of year.
The Lower Henry’s Fork: Anything below Ashton Dam gets too hot this time of year. Many other options in the area fish much better in July and August.
The Madison Drainage in YNP: The Madison, Gibbon, and Firehole rivers in Yellowstone National Park have geyser influences that warm their waters quicker than many others in the region. They are not worth fishing after July 1st and until the first cold spell in September. Please avoid these famous fisheries and their tributaries during this time of year.
Many lower-elevation lakes in the region are ineffective for fishing during the hot summer and can be dangerous for catching and releasing trout. Henry’s Lake is one of them because of how shallow the Lake is. I stay away until the first cold spell in September.
One important thing to note in this discussion is our personal responsibility to monitor water temperatures in our trout streams. While FWP and other agencies take action when water temperatures are high, they are often late to the party and can be lenient in their restrictions. I carry a stream thermometer at all times and invite you to as well. Not only does it help me minimize my impact on already stressed trout, but it also leads me to find good fishing in cooler water fisheries. I also avoid any fishery with hoot owl restrictions in place, whether you can fish before 2:00 pm or not. I do this as the fishing is often better in cooler fisheries anyway.
I’ll admit, one of my pet peeves is when other anglers fish streams in unsafe water conditions to catch and release trout. It’s downright disrespectful to the resource and not acceptable in my book. There is rarely a reason to fish in these conditions.
Maybe I’ll write an article in the future with a few tips on fishing when water temperatures are high, but right now, the best advice I can give is don’t do it.
Fish elsewhere, target different species, tie flies, go on a hike, and do anything but fish for trout during warm water conditions. It’s not worth the poor fishing you will experience anyway.
I hope you all are finding your way around the warm summer we are experiencing. This week’s high is 97 degrees here in Bozeman. Yellowstone just placed more restrictions on its waters, and our fishing options are dwindling daily. I am worried about what August will bring, but there will be fishing opportunities for those who are creative.
2 thoughts on “Fly Fishing and Warm Water Temperatures in Southwest Montana”
So you are saying to come to Montana in May or June. Got it!
Haha those are great months to fish in this area. Each summer month has fisheries that are in their prime, though July and August can be tough on Southwest MT. I am usually not fishing this area that often this time of year, traveling to YNP or Idaho to find cold water.
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