mountains prevent wet storms from moving, forcing air to rise and then cool. This cooling air cannot hold as much moisture, causing heavy precipitation (up to in rainfall annually) on the western flanks of the mountains, which leads to extensive forestation. Snowfall typically totals more than annually, amounting to snow still being present as late as July or August. In warmer months, melted snow runs off into lakes, keeping them especially full. Because the mountains are so tall, storm clouds may get stuck even as the rest of the storm moves onward, leading to snowstorms and freezing temperatures year-round. In extreme conditions, these storm cells might endanger hikers by means of strong winds, fog, snow, and rain that can potentially make hiking nearly impossible. On the eastern sides of the mountains, air warms as it drops, producing Chinook winds, considerably lower precipitation, and less forested landscapes. Because of these conditions, temperatures on the western sides of mountains are steady, whereas temperatures on the eastern flanks fluctuate wildly. Goat Rocks obtained its name from a population of mountain goats that can be observed around the mountain. Other fauna include marmots and pikas at high elevations. Deer and elk can be found below the timberline, including mule deer, mule deer-black-tailed hybrids, Roosevelt elk, and Rocky Mountain elk that were introduced from Yellowstone National Park in 1913. Black-tailed deer are especially common. Climbing and recreation Old Snowy Mountain and Gilbert Peak, two of Goat Rocks's peaks, are frequented by hikers and mountaineers. Both are considered remote summits, although Old Snowy Mountain is the more accessible of the two. This, coupled with its easier ascent, makes Old Snowy Mountain the more popular climb. There are several routes up the mountain, which take 5–6 hours, rising in elevation. Running for round-trip, Old Snowy can be scrambled or climbed using glaciers, although a trail exists. From the summit, mountaineers can see Mount St. Helens and Mount Rainier in the distance. Because this area has a lot of loose talus and rock, an avalanche hazard exists. The climb up Gilbert Peak was first completed by Fred G. Plummer in 1899. It also rises in elevation, lasting 6–8 hours and running for round-trip. Because the routes are longer and more technically challenging due to loose rock, scrambling Gilbert is generally considered more difficult than Old Snowy Mountain. Most climbers opt to mount Gilbert early in the climbing season