When I get to a river for a day of fly fishing the first thing I do is check the water temperature. I also look at the water and try to determine if there appears to be any insect activity.
I learned this information from fly fishing on the Madison River in southwest Montana for many years. During the month of August, you must fish early or late in the day to have much activity. The Madison, like many other rivers, warms up during the heat of the day and the fish apparently stop feeding. When this happens it’s time to quit until the river cools off in the evening.
How Water Temperature Affects Fly Choice
I’ve learned that if the water temperature is under 54 or 55 degrees Fahrenheit I’m going to have to fish subsurface with a nymph or a streamer to catch trout. On most rivers, insects don’t hatch on the surface to offer dry fly fishing until the water warms to this temperature range. However, when the water warms to above 62 degrees, fishing is pretty much over, whether you fish surface or subsurface.
What Kind of Thermometer Should I use?
I prefer to use a standard glass cooking thermometer with a loop at the top that you can tie a few feet of line to dangle it in the water. Walk a few paces out into the river to take the temperature by dropping the thermometer clear to the bottom for about 30 seconds.
We just happen to sell such a thermometer online or at the Jans Park Avenue store in the fishing department. Come in and check one out.
Written By: Jan Peterson