Over the weekend, the moon, Earth and sun will all come into alignment, causing the California coast to see unusually high tides, known as king tides.
The planetary confluence combined with the gravitational pull of the sun and moon will bring some of the highest and lowest tides of the year and could lead to localized flooding in some coastal communities, particularly the San Francisco Bay Area.
Though the NWS has issued beach hazard advisories in the Southern California region, no significant damage is expected.
"These tides will peak during the mid to late morning," the NWS said on Friday, adding that "the lowest low tides of the season will follow hours later in the afternoons." The king tides tidal readings are expected to peak on Saturday.
King tides are normal occurrences that can happen multiple times a year when a new moon or full moon are closest to Earth and Earth is closest to the sun.
They are of particular interest to environmental scientists, who say that while the tidal shifts are not a part of climate change, they do provide a glimpse of what higher sea levels could look like as a result of global warming and the damage that can cause local communities. They are indicators of how and where rising water levels can extend further inland, especially when they occur under storm conditions. And, in addition to increased flooding, encroaching waves erode beaches and cliffs, and raise coastal groundwater levels.
In August 2020, the California Legislative Analyst's Office reported:
"Scientific estimates suggest the magnitude of sea‑level rise (SLR) in California could be at least half of one foot in 2030 and as much as seven feet by 2100. Moreover, storm surges, exceptionally high 'king tides,' or El Niño events could produce notably higher water levels than SLR alone."
According to the same study, up to $10 billion worth of existing property in California is likely to be underwater by 2050. An additional $6 billion to $10 billion will be at risk during high tides.
California King Tide Project organizers are asking residents and visitors to photograph and share images of the phenomenon over the weekend, "to create a record of changes to our coast and estuaries." The photos will be added to a map of this season's king tides, according to the group.
The organization is also leading guided walks and activities for the public at various beaches over the weekend.