Checking Water Temperatures to Locate Stillwater Trout

I spend a lot of my fishing time out of a drift boat on a Northern California tailwater. I don't really pay much attention to water temperatures. The water being released from a dam stays pretty consistent. It's more about the flows. With stillwaters its a whole different story. It's all about water temperatures

By checking water temperatures we can eliminate non productive water. All fish have a preferred temperature range where they are most active. For most lakes that have rainbow trout, it is recommended to use a scale of 55F to 65F. When temperatures are in this range the trout’s metabolism will be at its peak and it should be feeding. Keep in mind that as water temperature increase, the trout's ability to hold oxygen decreases. As a result trout avoid high temperatures in excess of their comfort zone and will move to areas of the lake that have cooler temperatures, typically deeper or areas that have springs or inlet streams


With this information we may deduct that one of the most valuable tools in a stillwater kit bag is a thermometer. When this is attached to a cord you can probe and test water temperatures in different areas of a lake and different depths.This will help you locate trout.

You should start testing water temperatures in the shallow food rich areas around 10 feet deep. Lower the thermometer into the water and note the surface temperature. If it falls within the trout’s comfort zone chances are trout will be in the shallower littoral zone. Should the temperature exceed the range the shallow reaches will probably be avoided. Move out to deeper water between 10 and 20 feet and lower the thermometer into the depths. Allow it to adjust and then quickly raise it to determine the temperature. Continue eliminating high temperature water to find trout.

Rainbow Trout prefer temperatures in the range of 55 to 60 degrees F. Although they will tolerate temperatures as high as 65 degrees F.





Brown Trout can be found in water with much warmer temperatures in the range of 60 to 70 degrees F.



Brook Trout prefer cooler temperatures in the range of 52 to 56 degrees F.




Cutthroat Trout prefer temperatures in the range of 55 to 65 degrees F.




During the heat of summer the combination of bright light and high water temperatures usually drives trout into the deeper reaches, often over 15 feet deep.

When fishing in waters where the water temperatures are in the upper comfort zone zone for the trout species caught, be aware that if you hook up and play a trout hard it may be hard for it to recover as a result of lactic acid build up and the reduced dissolved oxygen. This may likely be a lethal for the trout.

When temperatures get this high it may be best to go fish a tailwater instead.