The Firehole River is a unique river, from its diverse structure to its range in water temperatures. Originating from Madison Lake on the eastern side of the Continental Divide, the Firehole flows North to the civilized area of Old Faithful and then on to join the Gibbon River to create the Madison River at Madison Junction. This upper section above Kepler Cascades can only be reached by foot and offers smaller brook trout that were introduced in the late 1800's. The Firehole River has several hot water Geysers that act as tributaries, adding water volume to the river and increasing water temperatures. The hot water is a double-edged sword. During fall, winter, and spring months it helps keep the water at a happy temperature for the trout and aquatic insects such as the Salmon flies. The water temperatures during summer months, depending on where you are fishing on the Firehole, can be too hot and drive the trout into colder tributaries such as Sentinel Creek. Most of the fish on the Firehole are rainbows and browns averaging 5”-12”, with an occasional 14”-16”. During October and November, there are above average rainbow and brown trout below Firehole Falls, averaging 16”-24” long. These large trout travel from Hebgen Lake to spawn in the Madison, Gibbon, and Firehole Rivers, making for memorable fishing.