- From high in Rocky Mountain National Park in north-central Colorado, the Big Thompson flows east through a canyon to the town of Loveland. Eventually it leads into the plains where the Big Thompson meets the South Platte near Greeley. This river supports a healthy population of small to medium sized fish, that are eager to take a fly. The Big Thompson Canyon is also an entertaining whitewater run when the flows are high enough.
Recreation - The Big Thompson River starts small and becomes a medium-sized meadow river after it leaves the heavily fished Lake Estes (in the town of Estes Park) and Big Thompson canyon. The Big Thompson River is subject to low flows and ice during winter months, which makes fishing difficult if not impossible. There is some fantastic dry fly fishing, starting in spring and continuing to early fall.
For rafting and kayaking the Big Thompson Canyon is the only ruinable whitewater on the river. It rarely has high water, but if it does you will be entertained. Boaters normally put in at the Idyllwilde Dam. Immediately after launching, you encounter the steepest and most continuous water of the run. There is a dangerous culvert bridge that must be portaged at high flows at Viestenz Smith Mountain Park. Additionally above the bridge, the water runs fast with only a few micro eddies to catch for the portage.
Climate - The Big Thompson River is situated in high mountainous altitudes. Persons coming from lower elevations should be aware that time is needed to adjust to the higher elevations.
Warm days and cool to freezing nights can be expected in the mountains during the summer. July and August are usually the warmest months. During this time afternoon thunderstorms are common. Be prepared for both warm and chilly weather, as well as for rain showers.
Being at high elevation and fueled mainly by melting snow the Big Thompson is a rather cold river. During the spring runoff the river is full of freshly melted snow, and the temperature of the water is especially cold.
Please make sure that you dress appropriately when participating in whitewater sports. Wear shoes that can protect your feet if you bounce off rocks or walk out of a canyon in the event of an accident. Wet suits are mandatory when air and water temperature added together total 100 degrees or less. If total is less than 80 degrees, a full set of waterproof or wool garments on top of the wet suit should be worn.
To access the Big Thompson from the East, get on Interstate 25 going north to Loveland. Then take Highway 34 west to Estes Park. This highway runs along the river where you'll encounter the meadow section, then canyon, then Estes Lake.