How to read a tide table

A tide table is a timetable for the ocean. It lists the moments the water stops rising and starts to fall (a high tide) and the moments it stops falling and starts to rise (a low tide), with the height of the water at each turn. Everything else you might want to know, from when a tidepool opens up to when a harbor entrance is calmest, can be read from those few rows once you know what they mean.

This page walks through a California tide table column by column, then shows how the water moves between the rows, and finishes with how to plan real outings around it.

The four columns

Every tide table on this site, and almost every one you will find elsewhere, has the same four pieces of information.

Type High or Low. On most of the California coast you get two of each per day, but not always: about once every two weeks a day has only three turns, because the cycle runs about 50 minutes longer than a calendar day and one turn slips past midnight into the next date.

Date The calendar day in local time. Because each turn arrives roughly 50 minutes later than the same turn the day before, a high tide at 11:40 pm today has no partner tomorrow; its successor lands just after midnight the following day.

Time When the water reaches its peak or trough, to the minute. Treat the minute as a center point rather than a promise. The water is nearly still for a while on either side of a turn, and wind and air pressure can shift the moment by several minutes (see When the tide doesn’t match the prediction).

Height How high the water stands at that moment, in feet above a reference level called MLLW, Mean Lower Low Water. 0.0 ft is not the sea floor and not "sea level"; it is the average height of the lower of each day’s two low tides. A reading of 5.8 ft means the water is 5.8 ft above that average low. A reading of −1.4 ft (a minus tide) means it has dropped 1.4 ft below it, exposing rocks and sand that are usually under water. The full story of that zero point is in MLLW and tide datums, explained.

A sample day

Here is what a spring-tide day can look like at Port San Luis (an example, not a forecast):

Tide	Time	Height
Low	5:42 am	−1.2 ft
High	12:18 pm	4.1 ft
Low	4:51 pm	2.6 ft
High	11:06 pm	6.3 ft

Read it like this: the morning starts with a deep minus tide, the best tidepooling of the day. The water then climbs more than five feet to a modest midday high, drops only about a foot and a half to an afternoon low that never really uncovers anything, and finishes with the day’s big high just before midnight. The two highs differ by 2.2 ft and the two lows by 3.8 ft. That inequality is the signature of California’s mixed semidiurnal tide, and it has its own page.

Time zones and daylight saving

NOAA computes its predictions in Coordinated Universal Time. This site requests everything in UTC and converts it to Pacific Time in your browser, so the times you see already include daylight saving: PDT (UTC−7) from March to November, PST (UTC−8) the rest of the year. If you compare against a printed tide book, check its header. Some printed tables stay on standard time all year, and in summer they will look an hour early next to this site.

The day the clocks change, the table looks odd but is correct: in spring one day has a missing hour and every turn after 2 am jumps forward; in fall one hour happens twice.

What happens between the rows

A tide table tells you the turns. It does not tell you that the water moves very unevenly between them, and that unevenness matters more than anything else for planning.

The rule of twelfths

Sailors have used a rule of thumb for centuries: over the roughly six hours from a low to the next high, the water rises by 1, 2, 3, 3, 2 and 1 twelfths of the total range, hour by hour. The first and last hours barely move. The middle two hours move half of all the water.

fig · rule of twelfths

On a 5.3 ft rise, that is less than half a foot in the first hour and more than 1.3 ft in each of the third and fourth hours. A rock ledge you could stand on at the start of the flood can be knee deep an hour later in the middle of it.

Two cautions. California’s mixed tide often breaks the rule: when a high and the low after it are nearly the same height, the "six hours" may be three or nine, and the water can hang almost flat for hours. And the rule describes height, not current. Use it as a feel for the shape, and use the hourly curve (the console’s Outlook timeline, or the observed vs predicted chart on Tide Intelligence) when the details matter.

Slack water

Around each turn the water level barely changes for a while. Mariners call this slack water, and it is when harbor entrances, river mouths and kelp channels are calmest. Strictly, slack refers to the current, and in narrow entrances the current often keeps flowing for a while after the height has turned. Inside San Francisco Bay, or at the Morro Bay and Humboldt Bay entrances, the gap between high water and slack current can be an hour or more. The table gives height; NOAA publishes separate current predictions for places where that difference is dangerous.

Flood and ebb

A rising tide is a flood; a falling tide is an ebb. The console marks the direction with an arrow and the word "rising" or "falling". An ebb running out of a harbor mouth against incoming swell makes waves steeper and closer together, which is why the bar at Morro Bay is most dangerous on a strong ebb with a big swell. A flood running with the swell lays them down.

Reference and subordinate stations

NOAA’s predictions are best at stations with a long record from a tide gauge. Twelve of the 17 stations on this site have one. Five (Half Moon Bay, Santa Cruz, San Simeon, Ventura and Newport Beach) have no real-time water-level sensor, and three of them, Santa Cruz, San Simeon and Ventura, are subordinate stations: NOAA does not publish full harmonic predictions for them. Instead it takes a nearby reference station’s highs and lows and applies fixed corrections, a few minutes earlier or later and a height ratio or offset. Those stations get only a high/low table, so this site draws a smooth curve between the turns and labels it as interpolated. More on how that works is in Where tide data comes from.

If your beach is between two stations, use the closer one and remember that high tide moves up the coast from south to north: it reaches San Diego a couple of hours before it reaches Crescent City.

Planning with a tide table

Tidepooling

Look for a minus tide in daylight. The lower the number, the more of the intertidal zone is exposed; −1.0 ft and below is very good, and the best days of the year reach about −1.5 to −2 ft. Arrive an hour before the low and leave as it turns. California’s lowest daylight lows fall in early morning from late spring through summer and in late afternoon from late fall through winter, so a winter tidepool walk often ends at sunset. The tidepool planner ranks the next two weeks for you.

Always face the ocean. A low tide does not stop swell, and the biggest single set of the hour can wash over a reef that has been dry for twenty minutes.

Kayaking and paddleboarding

Plan to paddle with the current and to be off the water before the afternoon wind. Launch near slack, ride the ebb out of a bay and the flood back in, and avoid entrances at mid-ebb, when the current is strongest. Low tide in an estuary like Morro Bay or Elkhorn Slough can leave you walking across mud flats, so check that your route still has water at the low.

Surfing

Many breaks have a preferred tide: reef and point breaks often turn on at low to mid tide, and some beach breaks close out at low and fill in on the push. "Push" means the rising tide, and the first two hours of a big push after a deep low change many spots quickly. Keep a note of which tide works at your break and match it against the table.

Fishing

Moving water feeds fish. The hours either side of a turn, especially the start of the flood after a low, are traditionally best in the surf and around harbor mouths. In a bay, the last of the ebb concentrates bait in the channels.

Beach walks and access

Some beaches, coves and coastal trails pass points that are only open below a certain height. Know the cutoff, add a margin for swell, and plan to be past the point well before the water returns. People are stranded every year on California beaches that were passable an hour earlier.

Where to read the table on this site

• The Conditions Console home page shows the next highs and lows with a countdown, the water level right now, and a 24 or 72 hour tide curve under the swell and wind.
• Tide Intelligence (/tides/<station>) has a 14-day calendar with spring and neap marked, moon phases, daylight shading and the tidepool planner.
• The Coast Map lets you scrub through 96 hours of tide, swell and wind for all 17 stations at once.

None of these are for navigation. They are predictions, and the sea does not always follow the prediction; here’s why.