When should I actually stop fishing for trout in summer?
Carry a thermometer and let it decide. A practical protocol used across North American trout country: below 18 °C (64 °F), fish normally; 18–20 °C (64–68 °F), fish early morning only — the daily minimum — land fish fast and keep them wet; at 20 °C (68 °F) and above, stop, full stop, and many fisheries agencies post "hoot owl" closures at exactly this threshold. Note the species spread: brook trout hit distress earlier, lake trout have usually already retreated below the thermocline where your surface reading is irrelevant, so summer heat is chiefly a rainbow-and-brookie stream problem. At 45°N latitude this typically means late July through mid-August mornings; farther south the danger window is far longer.
The full story
This answer is one piece of a longer lesson — setups, diagrams and the reasoning behind it.
More questions about Temperature & metabolism
Same topic, other species
- Do crappie really feed all winter? — Crappie
- A cold front just passed and the bite died — why, and how long until it recovers? — Largemouth Bass
- When is the water too warm to fish for muskie? — Muskellunge (Muskie)
- How can perch keep feeding all winter when bass shut down? — Yellow Perch
- Do pike feed in winter? — Northern Pike
- How hot is too hot for smallmouth? — Smallmouth Bass
- Do walleye feed in winter? — Walleye