This is a very common and important question, and rightfully so. Proper conditions will greatly increase the safety of the group, as well as increase the likelihood of summit success on a giant Cascade volcano. We’ll answer best we can with the understanding that it greatly depends on the current mountain snowpack and weather.
Historically and statistically, April-September can have some of the most stable weather on Northern California’s Mt. Shasta. Part of the Cascade mountain range, Mt. Shasta is a strato-volcano and on average receives over 500″ of snow per season. This snowpack is what creates good and saf(er) climbing conditions on the volcanoes. The snow provides an efficient and essential surface for climbing. As a Cascade peak, underneath all the snow lies an unstable rock surface. Optimally we climb when the snow still covers these loose rocks and the weather mostly stable. With proper timing we will climb when the snow is frozen in the wee hours of the night and early morning. Then typically, by 10:00 or 11:00 the surface has softened and makes for a quick and exciting descent with one of the longest glissades on the planet!
The primary factor is we want to climb Mt. Shasta when there is adequate snow coverage and a reasonable chance for high pressure and good weather. The current winter snowpack depths and weather patterns will ultimately determine when that is.
Unlike peaks to the south in the Sierra Nevada Range, we need the snow depth for safe and efficient travel. The old notion to wait for the snow to melt is a potentially dangerous solution and certainly a tedious challenge of uphill scrambling on loose, steep, rocks. We at SMG choose climbing routes in optimal condition and utilize several trailheads and aspects as conditions change throughout the year. We are on the mountain daily scrutinizing route conditions as they quickly change.
We recommend and regularly schedule summit climbs from April-September. A climb outside of this timeframe is certainly possible as a private and custom trip. In 35 years of guiding on Mt. Shasta,we’ve found best summit success in the spring and summer months.
April and May are generally considered early season and can have fantastic alpine conditions. We feel this is the best timing for true alpine climbing and ski mountaineering with all of the routes having excellent conditions. There may still be concerns of avalanche hazard in Avalanche Gulch, especially if we receive new snowfall, but the ridges are prime now. You will be on snow the entire trip, from the trailhead to the top. Weather tends to be a bit colder and the wind a bit stronger as compared to later in the season. The advantage is the scenery is absolutely stunning and there are far fewer climbers on the mountain. Casaval Ridge is the preferred route for climbing and this is the season for a summit climb and ski or snowboard descent! Our experience is that there is a 90% chance of climbable weather in May, and 70-80% in April.
June and July are peak season on the mountain. This is typically the best stable weather and adequate snowpack combo. Avalanche Gulch and the West Face are both in prime climbing condition at this time. In a big winter we may receive enough snow to allow climbing on the south side routes through August. In drought years, earlier is better. This is also the most impacted season, but anything is still possible; we have skied fresh powder in June and had snowstorms in July that dropped over 4 feet!
August and September can have excellent and stable weather on the mountain. The North side Glacier Climbs are perfect at this time. August can be hot, but over on the north side, it’s cooler and the glaciers in prime shape. We may see afternoon thunderstorms, but they are usually late on Mt. Shasta and infrequent. Avalanche Gulch is typically done at this point, but the Hotlum and Bolam Glaciers are perfect! The snow level and temps may be creeping up on the south side routes and these may be too melted to allow safe climbing with serious rock fall a real hazard. As we get deeper into September, the days are short, temps a bit cooler, and the chance for snow not uncommon. The route conditions will deteriorate and we’re usually finishing up by mid September.
Fall and Winter A climb is always possible however Fall often has very poor climbing conditions due to melted snow and glaciers. For those intent on an off-season climb, the Clear Creek route is a good choice. If one is resolved to experience whatever the mountain chooses to dish out, a winter expedition is a wonderful experience. Statistically, it is also the least likely time to be able to reach the summit. Severe, unpredictable weather and winds, extreme temps, deep, unconsolidated snow all make for a challenging winter ascent. This is the time to bring the backcountry skis and boards, Mt. Shasta is legendary for off-piste recreation.
We’ve had summer conditions in a January summit and fierce winter storms with powder skiing in July. One thing is for certain, there are few sites that equal the rugged beauty of Mt. Shasta in a storm; the clouds reveal a fresh landscape that will leave you breathless. Be prepared for all types of weather and temperatures, any time of year. Check the current weather and do not trust any forecast more than 2 days in advance, storms move quickly and can create whiteout conditions.