Guide

Reading a tide table on this coast

Checked September 24, 2026 against NOAA Tides and Currents and the Bureau of Land Management.

The Tides tile repeats NOAA’s predictions for the station nearest the town you are reading for. This page explains what the zero on that scale is, which stations on this coast are measured and which are worked out from somewhere else, and why the water is not always where the prediction says.

Zero is not the sea bed

Every tide height on this coast is measured from mean lower low water — MLLW — which NOAA defines as “the average of the lower low water height of each tidal day observed over the National Tidal Datum Epoch.” In plainer terms: of the two low tides most days bring, take the lower one, and average it over about nineteen years. That average is zero.

Because it is an average, roughly half of all lower low tides fall below it. A prediction of −1.5 ft is not an error; it is a tide a foot and a half lower than the long-run average low — the tide a tidepooler wants and a boat in Humboldt Bay’s shallows does not.

It also means a charted depth of 6 feet is 6 feet at MLLW. On a minus tide there is less water over it than the chart says.

Some stations have constants. Some are offsets.

NOAA separates stations with their own tidal harmonic constants from stations without. A harmonic station’s predictions “are generated directly from the harmonic constants.” A subordinate station has none, so NOAA predicts the highs and lows at a reference station and then applies time and height adjustments.

That is a difference in arithmetic, and it is not the same thing as whether there is an instrument in the water. The north coast board shows ten stations, the Mendocino coast board four stations — Westport, Noyo Harbor, Arena Cove and Green Cove, which its nine towns share between them — the Sonoma and Marin board twelve stations: Sea Ranch, Fort Ross, Bodega Bay, Dillon Beach, Tomales, Marshall, Inverness and Bolinas on the coast, and on Marin’s bay side Point San Quentin for San Rafael, Corte Madera Creek at Larkspur, Sausalito, and Angel Island across Raccoon Strait for Tiburon, and the San Mateo board six stations — on the coast Pillar Point Harbor, which seven of its eight ocean towns read, and Año Nuevo Island, which Pescadero reads; on the bay side Oyster Point Marina, Coyote Point Marina, the west end of the San Mateo Bridge, and the port of Redwood City, whose gauge at Wharf 5 reads in real time. That is not an omission: the tide-prediction catalogue was read out for every station between Bolinas and Santa Cruz on September 23, 2026 and forty-one of the forty-four it returns are inside San Francisco Bay. Three face the ocean and two of those three are in San Mateo County. The Santa Cruz board shows two stations, Santa Cruz and Moss Landing, and the Monterey board four stations: Monterey, Carmel Cove, Moss Landing again (a town here, an alias there) and Mansfield Cone, a reference station on the cliff below Gorda and the only prediction on forty miles of the Big Sur coast, so Big Sur itself reads Carmel Cove from nineteen miles. The San Francisco board shows six stations for nine rows — the Golden Gate, Ocean Beach, North Point at Pier 41, Rincon Point, Hunters Point and Yerba Buena Island — and nothing there is more than four miles from the row that reads it. The San Luis Obispo board shows two stations for ten towns: Port San Luis, the county’s reference station on the pier inside the breakwater at Avila, and San Simeon, predicted from it. Morro Bay has no NOAA station — not the harbour, not the back bay, not Cayucos: the catalogue was read for the whole county on September 24, 2026 and is empty between San Simeon and Port San Luis, so the harbour reads Port San Luis from fifteen miles, Cayucos from twenty and Los Osos from eleven, and the tide inside the harbour and up the back bay to Baywood runs later and smaller than the open-coast prediction says. The Santa Barbara board shows three stations for seven towns: Santa Barbara at Stearns Wharf, the reference for the channel, which the city, Montecito and Summerland read from a mile to six and Goleta and Isla Vista from eight and ten; Gaviota State Park; and Rincon Island, the oil island off Mussel Shoals across the Ventura line, which is Carpinteria’s water at five miles. Gaviota and Rincon Island are reference stations of their own, not offsets. The Ventura board shows three stations for five rows and none of them is live: Ventura harbour and Port Hueneme are both subordinate to Los Angeles — worked out from a station sixty miles down the coast, the first on this site predicted from somewhere off its own board — and Rincon Island again, this time for the Rincon coast at three miles. The Los Angeles board shows six stations for sixteen rows, and three of them are live: the Santa Monica pier, the outer harbour at San Pedro — the Los Angeles station itself, the one Ventura’s are worked out from — and the fire boat pier at Long Beach. El Segundo and King Harbor at Redondo are subordinate to Los Angeles, a few minutes behind it; Avalon is Catalina’s own reference station. Zuma, Malibu and Topanga read the Santa Monica pier from eighteen, eleven and five miles, because the catalogue has nothing on the Malibu coast. The Orange board shows five stations for eight rows and none of them is live: the Newport Bay entrance at Corona del Mar is a reference station of its own, Balboa Pier is subordinate to Los Angeles, and two are inner water — the Los Patos highway bridge over the Bolsa Chica channel, an hour behind the open coast, for Sunset Beach and Seal Beach, and the inside of the Santa Ana River mouth for Huntington Beach — and the tile says so on both. San Clemente’s is the first station on this site predicted from San Diego. Dana Point has no station and reads San Clemente’s at six miles. The San Diego board shows six stations for eleven rows and two are live: the Scripps pier at La Jolla on the open coast, and the San Diego gauge at Broadway in the bay, which three of the others are predicted from. Campland and Quivira Basin are inside Mission Bay and the Broadway gauge is inside San Diego Bay, and the tile marks all three inner water; Point Loma and Imperial Beach are the open coast. Oceanside to Del Mar has no station at all and reads La Jolla, from six miles at Del Mar to twenty-four at Oceanside. The East Bay board shows eleven stations, every one of them inside the Golden Gate and so inner water, and four are live: Alameda, the Chevron pier at Richmond, the Amorco pier at Martinez and Port Chicago on Suisun Bay. The tide reaches the far end of the strait over an hour after it turns at the Gate, and the tile’s times are each station’s own. The North Bay board shows five stations, one for each row and none of them live: the Mare Island Strait at Vallejo, Benicia, Suisun Slough, the Napa River at Napa and the Sacramento River at Rio Vista, the last a reference station of its own well up in the Delta. Of the eighty-five station rows on these boards — eighty-two stations, since three are shared by neighbouring boards — only Crescent City, Monterey, San Francisco at the Golden Gate, Port San Luis, Santa Barbara, Santa Monica, Los Angeles, Long Beach, La Jolla, San Diego, Alameda, Richmond, Martinez-Amorco, Port Chicago and Redwood City have a water level gauge reporting in real time. The Golden Gate gauge has been reading since 1854, the longest tide record in the Americas, and it is the reference every subordinate station on the bay is predicted from; this site reads its predictions, as it does every station’s. Humboldt Bay’s gauge is at North Spit, near the entrance, and the board does not show it as a town station; three of the bay’s stations are predicted from it.

The north coast boards’ stations

Del Norte and Humboldt, north to south. The other boards’ stations are named above, and each is on its own board’s tile.

The lag up the bay is real and worth knowing: the tide at Arcata Wharf turns most of an hour after it does at North Spit. Read the station for where you will be, not the one nearest the entrance.

The Lost Coast Trail runs on the tide table

South of Petrolia, the Bureau of Land Management’s King Range trail follows the beach, and parts of it go under water. BLM: “Be aware of the tide! Carry a tide table and hike these stretches during an outgoing tide of three feet or less to avoid being trapped.” The stretches it names are near Punta Gorda, Sea Lion Gulch to Randall Creek, and Miller Flat to Gitchell Creek.

BLM’s trip planning guide is more exact, and stricter in one place: Punta Gorda passable under about 6 feet, Sea Lion Gulch to Randall Creek under 2.5 feet, entered only on a falling tide, and Miller to Gitchell under 3 feet. The King Range tide flyer names the station to read: Shelter Cove, 9418024 — the one this board shows for Shelter Cove and Petrolia.

Why the water is not where the prediction said

NOAA is direct about the limits of a tide table:

On this coast those are routine. A winter storm’s wind and low pressure hold the sea higher than predicted. Rain down a river — on the north coast the Eel, the Mad, the Klamath or the Smith — raises the level in the lower rivers and sloughs and can hold the ebb back. And a big swell pushes water far higher up a beach than any tide height: the Eureka weather office warns that sneaker waves “can strike without warning”, on any tide. A three-foot tide on the table is not a three-foot beach.

Where a station has a live gauge, the observed level is the answer; where it does not, treat the prediction as the start of the question.

Sources

• NOAA Tides and Currents, tidal datums — the definition of MLLW
• NOAA Tides and Currents, page help — harmonic and subordinate stations in NOAA’s own words
• NOAA Tides and Currents, frequently asked questions — what a prediction can and cannot include
• Bureau of Land Management, Lost Coast Trail and King Range trip planning guide — the impassable zones and their tide heights
• National Weather Service Eureka, beach safety brochure
• Station pages for the north coast boards: Pyramid Point, Crescent City, Trinidad Harbor, Mad River Slough, Arcata Wharf, Samoa, Eureka, North Spit, Fields Landing, Eel River, Shelter Cove