Weather

Weather patterns in Missoula originate from the Pacific Costal regions.  This means that the wind, rain and snow we see usually arise over the Pacific Ocean in the west and move east across the state.  Only about 14 inches of rain falls each year, so it is fairly dry.  It is interesting to note that Pattee Canyon has quite different vegetation than the Missoula valley.  The rain and clouds often become trapped in the canyon, causing the spring months to be 80% wetter than the rest of Missoula!

See the climate graph and charts!

Geology

The rocks that form the "basement" for the Rocky Mountains, including the ranges in Missoula, are 2.5 to 3 billion years old.  They are mainly igneous and metamorphic rocks called gneiss, schist and granite.  In the Paleozoic Era (600 to 225 million years ago) shallow seas covered the area and eventually the sandy bottoms turned into sandstone, a sedimentary rock.  135 million years ago, mountain building began, forming the Rockies.  Over time, there has been much erosion and weathering of the rocky faces, and eventually the streams and rivers that we see now developed.

The Missoula valley is also unique because of the massive Glacial Lake Missoula formed by an ice dam on the Clark Fork River.  This lake stretched from Sandpoint, Idaho to Butte, Montana and was over 1000 feet deep in Missoula.  The shorelines are still visible on Mount Jumbo and Sentinel.  When the Glacial Lake drained, much of eastern Washington and Oregon were scoured as hundreds of feet of water rushed at speeds reaching 60 miles per hour!  More Information

Vegetation

The most common species of trees in Pattee Canyon are the Ponderosa Pine, Douglas Fir and Western Larch.  On the upper slopes we can see many Lodgepole Pines as well.  There are also many shrubs in the canyon, including mock orange, ninebark, snowberry and mountain maple.  It is interesting to note how both the geology and climate can affect which plants go where.  For example, north faces of mountains usually have more large trees than south faces.  Why do you think this happens?