Middle Fork Salmon River Weather
The weather of this area during the fly fishing and Middle Fork Salmon River rafting trip season (June – September) is generally dry during the summer, hot during the days, cool at night, with some unpredictability due to the elevation of the terrain around the river. The Middle Fork flows out of the Sawtooth Mountains and carves ever downward through the mountain ranges of the Idaho batholith (Bighorn Crags, Tango Mountains, Salmon River Mountains, Yellowjacket Mountains). One of the most unique and special things about the Middle Fork is that we begin high up in the sub-alpine ecosystem beneath the high 10,000’+ peaks of the Sawtooth Mountains, and descend over 3000ft of elevation into the deep canyon environments during the course of a 6 day, 100-mile river trip. We get a full profile of Idaho’s geography and ecosystems. This also means that temperatures can vary well over 10F degrees between the upper and lower sections of the river.
Weather in the Third Deepest Canyon in the Country
Due to the geographic and geologic nature of the Middle Fork canyon, we tend to experience both warmer than forecasted nighttime temps as well as un-forecasted weather.
These warmer temperatures occur from the concave shape of the canyon which is carved out of “low albedo” rose granite. Low albedo means that the rock retains the sun’s heat and radiates it back out during the night. This is the reason that we see most Native American heritage activity near large granite formations, where they knew the rocks would keep them warmer throughout the night.
Floating through the 3rd deepest canyon in the country also means that we are always in close proximity to the high peaks which define the ruggedness of the Frank Church Wilderness and create the mountainous canyon rim. The deepest place in the Impassable Canyon is Cradle Creek, one of our favorite camps, which is nestled below more than 7000ft of vertical relief. From a micro-meteoroidal perspective, this means that as air masses are pushed up over these high mountains and sometimes create unforeseen weather such as a rogue thunderstorm or passing rainstorm. In the summer in Idaho, a little rain is always welcomed!
One of the most memorable and perhaps spiritual experiences is being in the bottom of the Impassable Canyon on a hot day when a thunderstorm passes overhead. The power of the thunder shakes you to your core in a spiritual way, and a quick deluge provides a welcome relief from the summer heat. In the summer these storms can come and go within 30 minutes, and the return of quiet and sunshine on the refreshed, glistening canyon is truly surreal.
Typical Weather on the Middle Fork
|Mean Max High||Mean Min Low||Average Temp||Days of Precip||Average Precip||June||77||46||60||10||1.42"|
How to Check the Forecast for Your Middle Fork Trip
For the first half of your trip, you can either check the forecast on the NOAA direct link or plug this latitude and longitude into your preferred weather site: 44.76219729303162, -115.1061940355058.
For the second half of your trip, you can either check the forecast on the NOAA direct link or plug this latitude and longitude into your preferred weather site: 45.09453352089491, -114.73305589181766.
Nearest weather stations for Upper section of Middle Fork:
Nearest weather station for lower section of Middle Fork:
Weather Underground forecast for Salmon, Idaho.
Additional Useful Info
Where your trip starts:
June and early July: Boundary Cr Boat Ramp, River Mile 0, 6,300’ elevation. Google Maps link.
Mid-July & August: Indian Cr Wilderness Airstrip, River Mile 24; 4,900’ elevation. Google Maps link.
September: Thomas Cr Airstrip, River Mile 35; 4,300’ elevation. Google Maps link.
For more information about useful items to pack on your trip, see our blog post on What to Wear Salmon River Rafting.