SAN DIEGO (FOX 5/KUSI) — The fall equinox not only marks the first official day of fall, here in San Diego it is also the time to view "Salkhenge." However viewers did not get a chance to see the rare phenomenon this year as clouds obscured the view. Sunday, Sept. 22, 2024 is the first day of fall and also the start of shorter days and longer nights in the northern hemisphere. A rare sight to see: ‘Scrippshenge’ sunset awes San Diego During the fall and the spring equinoxes, the setting sun perfectly aligns with the Salk Institute's "River of Life" water feature. Sunday night, the rare phenomenon happened once again, but was not visible as clouds blocked the view. Clouds obstruct view of ‘Salkhenge’ at sunset on Autumn Equinox on Sept. 22, 2024 (FOX 5/KUSI)Salk Institute's "River of Life" water feature ahead of "Salkhenge" on Autumn Equinox Sept. 22, 2024 (FOX 5/KUSI) Salk Institute's "River of Life" water feature ahead of "Salkhenge" on Autumn Equinox Sept. 22, 2024 (FOX 5/KUSI) The Salk Institute in La Jolla is an independent, nonprofit research institution, founded in 1960 by the developer of the first safe and effective polio vaccine -- Jonas Salk. Unique sunset called ‘Salkhenge’ takes place in La Jolla Now, Salk scientists work to make discoveries in the fields of aging, cancer, neuroscience, immunology, climate change, plant science, metabolism, biochemistry/biophysics and computational biology. "Salkhenge" at sunset on March 19, 2024 (Credit: Salk Institute) According to the institute, Jonas Salk compared the River of Life to representing "the trickle of knowledge produced by this facility, spilling out into the body of knowledge, symbolized by the ocean. Thus, we feel a connection to a higher purpose." A ‘Scrippshenge’ parallel: Crescent moon winks above Oceanside Pier The Salk Institute, a not-for-profit research institute described as one of the most significant architectural sites in the United States, offers architecture tours.  All proceeds from the Architecture tour program support the Institute’s conservation efforts. The Salk Institute is located at 10010 N Torrey Pines Road in La Jolla.