Water temperature and rainbow trout

If you are only going to watch one factor to understand when the fishing is good, let it be water temperature. Rainbow trout is a cold-water fish, and the degrees steer everything: how active it is, where in the water it stands and how it wants you to fish. If you learn to read the temperature you also understand why some days explode and others stand still.

Rainbow trout’s favourite temperature

Rainbow trout thrives and is most active in cool, oxygen-rich water around 10 to 14 degrees. In that range it eats willingly, moves over larger areas and often chases active baits. It is no coincidence that spring and autumn are peak season, because then the water often sits right there. The farther the temperature slides from that range, the more sluggish the fish becomes, in both directions.

When the water gets too warm

When the surface temperature creeps over 18 to 20 degrees the water loses oxygen and the rainbow trout grows lazy. It in practice stops hunting in the warm surface water and instead seeks cooler, oxygen-rich pockets: deep holes, around inlets where fresh water comes in, and in the shade under trees and jetties. In summer that means you should fish early and late, go deep in the middle of the day and deliberately look up the cool stretches. More under put and take in summer.

When the water is cold

In really cold water everything goes slower, but the fishing is far from dead. The fish often stands deep and gathered, takes sluggishly and moves little, so you need to drop the tempo a lot. Fish slowly with quiet baits, give the fish plenty of time and be ready for a take that can be almost invisible. Under the ice, ice fishing is its own branch, see put and take in winter.

Use the temperature as a tool

Make a habit of feeling the water when you arrive, or use a simple thermometer. If it is around 10 to 14 degrees you can fish actively and search. If it is warmer, go deeper and slower and look for cool water. If it is cold, slow everything down. How the temperature follows the seasons you see in put and take through the year, and how it plays with the day in when they take.