Steelhead and water temperature

A thermometer is an important piece of a steelheader’s equipment and will help to unlock some of the mysteries of a river. The optimum water temperature range for steelhead is 42 to 58 degrees F. Within this range, 50 to 55 is ideal. What this means to an angler is that within the optimum range, steelhead tend to be most aggressive and capable of moving a long distance to intercept or chase a fly. This temperature range can be found on most Great Lakes rivers from late September through November. That is why I prefer that time of year for steelhead fishing. In the fall, steelhead are spread throughout the river in a wide range of water and are susceptible to a range of angling techniques. Normally, fall water temperatures need to fall into the mid 60s before steelhead enter the stream or river. 
 
But actual water temperature does not always tell the entire story. The direction of the mercury often has a great significance. Cold fronts that blow through the Great Lakes region can reduce air temperatures by 20 degrees in a short period of time, causing water temperatures to drop by 5 to 10 degrees or even more overnight. Streams and rivers with a predominance of bedrock are particularly susceptible to wide temperature changes. Rivers that have more groundwater influence or that run out of an impoundment or large body of water may not have such dramatic changes.
 
A significant decrease in water temperature will slow steelhead activity. Therefore, fishing is often more difficult after a cold spell, especially for swinging flies, so I try to avoid fishing the early morning hours after a cold night. A number of times a cold front has moved through in the late morning or early afternoon while I was on the river, and as the water temperature dropped throughout the afternoon, so did the number of fish interested in taking a fly. 
 
Rising water temperatures have the opposite effect. Even a small to moderate increase in the water temperature can have a positive impact on steelhead activity. Based on the notes in my fishing log and my observation, some of the best steelhead fishing coincides with stable or rising water temperatures. I try to time my outings to meet such conditions. After a very cold night, I prefer to fish the late morning and early afternoon, allowing the water temperature to recover. I also do my best to select days to fish when temperatures will be on the rise as opposed to falling.
 
You can still find quality steelhead fishing even when the water temperatures isn’t in the optimum range. During winter months, you can seek out solitude on most rivers, and an understanding of water can play an important part in your success. When water temperatures drop into the 30s, a steelhead’s metabolism begins to decrease. This generally causes steelhead to hold in slower water or flows that are out of the main current.
 
Steelhead can remain quite active during the winter months, especially when the water temperature is fairly stable. I have had good success swinging flies in 33- to 35-degreee water that has held stable for a time. Given the fish’s slower metabolism, presenting a swinging fly in a slow, controlled fashion will work best in the winter. Steelhead will generally not chase a fly as far or with the same aggressive manner as they do when temperatures are in the optimum range. 

​Excerpted from Advance Fly Fishing for Great Lakes Steelhead by Rick Kustich