Red Slate Mountain
Peak · 13,139 ft · Mammoth Lakes corridor
Red Slate Mountain rises 13,139 feet in the Mammoth Lakes corridor of California's Sierra Nevada. A high alpine peak with avalanche terrain, it demands winter caution and rewards calm-morning ascents with low crowds.
Wind averages 15 mph across the month but gusts to 43 mph by afternoon; morning ascents stay calmer. Temperatures hover near 23 degrees Fahrenheit. Snow and exposure dominate spring and early summer; route-finding on loose rock and scree is typical on dry approaches. Expect solitude; base popularity sits at 0.2.
Over the past 30 days, Red Slate Mountain has averaged a NoGo Score of 36, with wind at 15 mph and temperatures near 23 degrees. Conditions have held steady through the rolling 90 and 365-day averages. The week ahead will test afternoon wind gusts against morning windows; crowding remains negligible, so timing is about safety and daylight rather than parking.
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About Red Slate Mountain
Red Slate Mountain sits in the high Sierra east of the Sierra crest, above the Mammoth Lakes basin. Access is via US 395 to Mammoth Lakes, then local roads toward the Inyo National Forest boundary. The peak anchors remote terrain with minimal trail infrastructure; most approaches traverse off-trail through alpine meadow and scree. Winter and spring climbers must assess avalanche hazard through the Eastern Sierra Avalanche Center (ESAC) forecast. The 13,139-foot elevation places it above treeline with full exposure to upper-atmosphere wind and weather.
Spring and early summer bring lingering snowpack and unstable slab potential; late September through October offers the most stable snow-free window. Temperatures range from a 365-day low of 10 degrees Fahrenheit to a high of 36 degrees. Wind averages 15 mph over the past month but maxes at 43 mph, typically arriving by afternoon. Crowding averages just 2.0 on a 10-point scale, reflecting the peak's low base popularity and technical approach. Afternoon thermals and shadow patterns shift rapidly at this elevation.
Red Slate Mountain suits experienced mountaineers and scramblers willing to navigate exposed terrain and manage avalanche risk. Summer parties plan for rock scrambling and routefinding; winter ascents demand snow-climbing gear and belay anchors. The sparse crowds mean no permit system or parking constraints; solitude is nearly guaranteed. Head here on stable, high-pressure mornings when wind is light and visibility extends across the Sierra crest. Avoid afternoon departure times and descents when wind peaks.
Nearby summits in the Mammoth corridor include the Ritter Range and Banner Peak to the west, accessible via different drainages but similar elevation and exposure. Red Slate Mountain's lower profile and isolation make it a quieter alternative to more-trafficked peaks in the Inyo. Winter and spring parties often pair it with reconnaissance of adjacent spires and couloirs. Summer ascents work best as part of a multi-day high-Sierra traverse rather than a single-day summit push.