1981 – The last U.S. avalanche with comparable casualties occurs on Mount Rainier, killing 11 climbers and establishing a benchmark for the severity of the 2026 Lake Tahoe event [6][9][13].

Jan 2026 – A fatal avalanche strikes the Castle Peak area, underscoring the region’s ongoing snowpack instability and foreshadowing the February disaster [7].

Jan 2026 – A snowmobiler dies in a separate avalanche at Johnson Peak/Castle Peak, adding to the recent string of backcountry fatalities in the Sierra Nevada [7].

Feb 17, 2026 – 6:49 a.m. – The Sierra Avalanche Center issues an avalanche watch for the Castle Peak backcountry, warning of possible large slides within 24‑48 hours [9][10][13].

Feb 17, 2026 – 5:00 a.m. – The watch upgrades to an avalanche warning, urging travelers to avoid avalanche terrain just hours before the group departs the trailhead [9][10][13].

Feb 17, 2026 – 11:30 a.m. – A D2.5 “football‑field‑size” avalanche erupts on the north‑facing slope near Castle Peak, burying eight skiers, leaving one missing, and rescuing six survivors after they activate beacons and an iPhone SOS [1][5][6][9][11][13].

Feb 17, 2026 – shortly after 11:30 a.m. – Roughly 50 specialized responders, including snowcats and ski units from Boreal Mountain, Tahoe Donner’s Alder Creek, and local sheriffs, navigate whiteout conditions and gale‑force winds to reach the site [1][2][6][7].

Feb 17, 2026 – afternoon – Sheriff Wayne Woo notes that a rescuer’s spouse is among the deceased but affirms the team’s commitment to rescue and recovery, while Capt. Russell “Rusty” Greene says the slide overtook the party “quickly” and warns the search will be “slow and tedious” [2][13].

Feb 17, 2026 – evening – Governor Gavin Newsom posts on X that the avalanche is a “horrible tragedy,” his office coordinates an all‑hands state SAR effort, and Nevada County Sheriff Shannan Moon announces a transition to a recovery mission for the eight victims [5][3].

Feb 18, 2026 – Crews recover eight bodies but leave the ninth victim’s remains buried because ongoing whiteout, 3‑6 feet of new snow, and high avalanche danger prevent safe retrieval; the Sierra Avalanche Center maintains a high‑danger warning through Wednesday [4][9][11].

Feb 18, 2026 – Forecasts call for an additional 1‑4 feet of snow Wednesday night through Thursday, raising the risk of further slides and delaying body recovery until a possible brief reprieve on Friday‑Saturday [4][9].

Feb 19, 2026 – Blackbird Mountain Guides suspends all field operations through at least Feb 22, 2026, launches an internal investigation, and pledges support for victims’ families while urging the public to avoid speculation [4][8].

Feb 19, 2026 – The Northwest Avalanche Center warns that a heavy‑snow system expected next week could elevate avalanche danger in the Cascades, echoing the California tragedy and urging travelers to check nightly forecasts [12].