Yosemite National Park has renewed its alert about the Yosemite summer branch drop season, weeks after the July 2025 death of 29-year-old Angela Lin, who was struck by a falling limb from a giant sequoia during a hike through the park’s Tuolumne Grove. The warning, posted on the park’s social media channels on Monday, sets out the conditions under which healthy-looking trees shed large branches without warning and advises visitors on how to reduce their exposure.
What the summer branch drop warning covers
Summer Branch Drop (SBD) is a seasonal phenomenon in which a structurally sound-looking tree suddenly loses a limb, oftentimes without warning, according to the park’s alert. Yosemite says the hazard occurs most frequently in black oaks across the park and is most common during hot, calm afternoons when there is no wind.
The park’s guidance identifies several characteristics that distinguish SBD events from wind-caused branch failures. Breaks typically occur three to 12 feet from the trunk along the branch’s length, rather than at the point where a branch connects to the trunk. Failed limbs are usually long and horizontal, frequently extending to or beyond the tree canopy. Many of the falling branches appear sound, though some show signs of wounds or decay. Older and less vigorous trees are more prone to SBD, and a tree that has already shed a limb in this way is considered more likely to lose another.
Angela Lin, a software engineer who had worked for about six years at Salesforce and then Google, was killed in July 2025 when a branch from a giant sequoia struck her on the head during a hike with friends, according to the New York Post. Her death prompted the park to re-examine how it communicates the summer branch drop risk to visitors.
Yosemite is clear that SBDs are unpredictable and cannot be precisely forecast. However, the park has issued practical guidance for visitors who want to manage the risk while in the field.
Safety steps the park recommends
The park urges visitors not to leave immobile people, such as infants or elderly individuals, directly under large oak trees. Sitting or pitching a tent beneath these trees on hot days is strongly discouraged. Visitors are advised to listen for loud cracks overhead and, if they hear one, to move quickly away from the tree rather than towards it. Reporting any branch or tree drop to a park ranger is also recommended, as it helps staff monitor and assess tree health across the park.
Branch drops are one layer of a broader safety picture at Yosemite. The National Park Service records rockfalls as a separate hazard: while relatively uncommon, they occur several times in Yosemite Valley each year and can cause serious injury or death. The NPS advises extra caution on or immediately below cliff faces, where the risk is concentrated.
Lightning is described as more common than rockfall, particularly on summer afternoons. The park’s guidance states that there is no safe shelter outside and recommends that visitors seek a substantial building or a hard-topped vehicle during a storm. Wood smoke from campfires is also flagged as a health concern, with Yosemite warning that smoky conditions peak from spring through autumn due to planned and unplanned fires, and that elevated emissions may pose serious health risks for sensitive individuals.
Yosemite’s broader safety record
The park’s standing as one of the more hazardous destinations in the US national park system gives the summer branch drop warning wider context. Yosemite recorded 179 deaths between 2007 and 2024, placing it third among US national parks by fatality count, behind Lake Mead National Recreation Area (317 deaths) and Grand Canyon National Park (198 deaths), according to data from personal injury firm Panish Shea Ravipudi LLP.
The leading cause of death in Yosemite is accidental falls or slips, which makes hiking and climbing the riskiest activities in the park. NPS data covering 2019 to 2023 also records selfie-related incidents near waterfalls, drownings, motor vehicle accidents, and medical emergencies as recurring causes of visitor fatalities.
Sudden changes in weather conditions and water currents add to the risk profile, particularly for visitors unfamiliar with the terrain. The park’s advice across all hazard categories returns to a single principle: ‘In Yosemite, and in any natural area, it is up to you to be aware of your surroundings.’ With the summer branch drop season now formally open and the Lin case still fresh, the park’s operations team says it is asking visitors to report any downed limbs to rangers so that affected trees can be assessed and monitored without delay.
