The term comes from wildfire country. Early twentieth-century logging crews worked predawn "hoot-owl" shifts because forests were too dry to cut safely by afternoon. Montana Fish, Wildlife & Parks borrowed the idea: when a river hits 73°F for three consecutive days, angling shuts down from 2 p.m. to midnight. Trout don't die at 73. They start dying around 77. But a fish caught and released above 68 is far more likely to die afterward, so the state set the trigger four degrees below lethal.
This summer, FWP has restricted roughly 1,200 river miles across more than twenty systems, earliest closure July 3. Montana has imposed these restrictions six summers running now, each year covering more water. They lift when temperature and flow recover. FWP won't pull them for one cool day if the heat's coming back.
Trigger: 73°F for three consecutive days on USGS or FWP gauges. Native cutthroat reaches use a lower 66°F threshold, adopted in 2022.
Restricted hours: 2 p.m. to midnight. Most guides already quit by early afternoon in midsummer.
Full closure: Some stretches shut down entirely. The Madison below Ennis Reservoir hit 70–71°F even at night.
Yellowstone NP: Manages for native cutthroat with a 68°F trigger. Park rivers reached 80–86°F in July 2026. Dead fish reported in the Firehole.
Six-year pattern: Restrictions every summer since 2021. Scale has grown from targeted stretches to 1,200 miles statewide.
