Western US Trout Rivers Face Heat-Driven Fishing Closures

Record heat across the western United States is turning iconic trout rivers into warm, low‑oxygen streams. Wildlife agencies in Yellowstone National Park, Colorado and Montana have instituted temperature‑ and flow‑based triggers that automatically close or limit fishing during the hottest afternoon hours. Colorado has placed restrictions on 19 rivers covering more than 600 miles this summer, while Montana has limited about 1,200 miles, using the so‑called “hoot‑owl” rules that ban angling after 2 p.m. when water temperatures exceed set thresholds. These measures aim to protect trout from lethal conditions but have become routine, affecting working anglers and local economies.

A separate forecast for the Missouri River notes that, despite the broader heat wave, water temperatures remain moderate (around 65 °F) and no closures are expected for August. The report highlights typical summer conditions—high air temperatures, occasional thunderstorms, and weed growth—but confirms that the river’s flow and temperature are currently within safe limits, offering a contrast to the stricter shutdowns elsewhere in the West.