Marin Tide Questions
When are the king tides in Marin?
King tides in Marin come in winter, mostly in November, December and January. They are the highest tides of the year and happen when a new or full moon lines up with the moon's closest pass to Earth. The highest water usually comes in the middle to late morning. See the king tides guide for this season's dates and the roads that flood.
Where does Marin flood during king tides?
Most tidal flooding is on the bay side. Highway 1 at the Manzanita Park and Ride near Mill Valley, Gate 5 Road in Sausalito, the Canal neighborhood in San Rafael, Lucky Drive near Larkspur and North San Pedro Road near China Camp are the usual spots. On the coast, Calle del Arroyo in Stinson Beach is often hard to pass. Never drive through flooded roads.
Why are there two high tides and two low tides a day?
The moon's pull raises a bulge of ocean on the side of Earth facing it, and a second bulge forms on the far side. As Earth turns, Marin passes through both bulges and both low spots between them in about 24 hours and 50 minutes. That gives two highs and two lows, and each day's tides come about 50 minutes later than the day before.
Why are the two high tides different heights?
California has mixed semidiurnal tides, so the two daily highs and the two daily lows are different sizes. Tide charts call them higher high, lower high, higher low and lower low. The gap can be several feet in one day. For tidepools and beach walks, the lower low is usually the one that matters. How to read a tide chart explains the pattern.
What is a minus tide?
A minus tide, or negative tide, is a low tide that drops below 0.0 feet on the tide chart. Zero is mean lower low water, the average of the lowest low each day. Minus tides come in runs of a few days around the new and full moon, and on the Marin coast the deepest reach about 2 feet below zero. Read more in the minus tides guide.
Why is low tide in the morning in summer and the afternoon in winter?
The lowest tides of each month come near the new and full moon, and the time of day they land on slowly shifts through the year. On the Marin coast, the deepest lows of late spring and summer fall between before dawn and mid-morning. From late fall through winter they move to the afternoon and evening, often close to sunset in November and December.
What is the best time to go tide pooling in Marin?
Go on a minus tide in daylight. The National Park Service suggests arriving at least an hour before low tide and leaving no later than an hour after the water starts to rise. In Marin that usually means early mornings from April through July, or afternoons from late fall through February. Check the time at the station nearest your beach.
Where are the best tide pools in Marin County?
Duxbury Reef at Agate Beach in Bolinas is the largest tidepool area in Marin, a wide shale reef with a slow rising tide. Sculptured Beach, about two miles south of Limantour Beach, has the best and safest pools inside Point Reyes National Seashore. See Duxbury Reef tides and the tide pools guide.
Can you collect shells or rocks at Duxbury Reef?
No. Duxbury Reef is a State Marine Conservation Area, and it is illegal to injure, take or possess any living, geological or cultural marine resource there. That includes shells, rocks, sea stars, crabs and seaweed. The only exception is fishing for finfish from shore with a license, per the California Department of Fish and Wildlife.
Why is low tide dangerous on the Marin coast?
A low tide draws people out onto rocks the ocean usually covers, where sneaker waves can knock them down without warning. Tidepoolers have died at Point Reyes beaches this way. The rising tide can also cut off the way back at Sculptured Beach and McClures Beach. Never turn your back on the ocean, and head back before the water turns.
Is the tide later in Tomales Bay than on the coast?
Yes. The tide takes time to travel up the bay. On average, NOAA predicts high and low tide at Inverness about an hour and a half later than at Point Reyes, and Marshall a little later still. Use the station nearest your launch, such as Inverness or Tomales Bay, rather than a coastal one.
Is the tide in Sausalito the same as at Stinson Beach?
No. The tide reaches the outer coast first and arrives later inside San Francisco Bay. On average, NOAA predicts the tide at Sausalito about 25 minutes after Point Bonita at the Golden Gate, the station used for Stinson Beach, and about 50 minutes after Point Reyes. Heights differ too. Check Sausalito tides and Stinson Beach tides separately.
What does MLLW mean on a tide chart?
MLLW stands for mean lower low water. It is the zero line on US tide charts, set as the average height of the lower of the two daily low tides over a 19-year period. A 6.0 tide is six feet above that line. A -1.0 tide is a foot below it, which is what tidepoolers call a minus tide.
What is the difference between spring and neap tides?
Spring tides have the biggest range of the month and come near the new and full moon, when the sun and moon pull in line. Neap tides have the smallest range and come near the quarter moons. Both happen twice a month, all year. On the Marin coast the daily range runs from about 4 feet at neap tides to more than 8 feet at spring tides.