Where do the tide times come from?

From NOAA's Center for Operational Oceanographic Products and Services (CO-OPS), which publishes the official tide predictions for the United States. Harmonic stations are predicted from their own tidal constituents; subordinate stations from a nearby harmonic station with NOAA's time and height corrections. Water levels are measured every six minutes at NOAA's water level stations.

What does MLLW mean, and why are some low tides negative?

Heights are in feet above mean lower low water (MLLW): the average of the lower of each day's two low tides over NOAA's 19-year tidal epoch. It is the zero of US tide tables and nautical charts. A low tide below that average, common near a new or full moon, is printed as a negative height.

Why is the water higher or lower than the tide table?

Predictions are astronomical: they account for the moon and the sun, not the weather. Onshore wind, low air pressure and high river flow raise the water above the prediction; offshore wind and high pressure lower it. At a water level station the page shows the difference, measured less predicted, as storm surge.

What are spring and neap tides?

Spring tides are the largest ranges of the month, with the highest highs and lowest lows, and come a day or two after the new and full moon, when the sun and moon pull in line. Neap tides, the smallest ranges, follow the first and last quarter moons.

Tide times and tide charts

Today’s high and low tides, 7-day tide tables and tide charts for 3,252 NOAA tide stations on every US coast, with the water measured live at 233 of them against the prediction, storm surge and coastal flood levels.

Major harbors

The next high and low tide, local time, feet above mean lower low water.

By state and territory

East Coast

Gulf Coast

West Coast

Alaska and Hawaii

Territories

What is here

Tide tables: Every high and low tide at every NOAA tide prediction station, for today, the next seven days and any month, in the station's own time, with sunrise, sunset, moonrise and the phase of the moon.
Tide charts: The predicted tide through the day, every six minutes at a harmonic station, with the present moment marked.
Water levels: At NOAA's water level stations: the water measured over the last 48 hours against the prediction, the storm surge, the National Weather Service's coastal flood levels, and any coastal flood advisory or warning in force.
Datums: Mean higher high water, mean sea level and the other tidal datums, the highest and lowest water ever measured, and the range of the tide.

Common questions

What is a harmonic station, and what is a subordinate one?

A harmonic station has a long enough record for NOAA to resolve the tide into its constituents, and its tide is predicted every six minutes from them. A subordinate station is predicted from a nearby harmonic station by adding NOAA's time differences and scaling its heights, and has only its highs and lows. Its curve here is drawn between them.

How far ahead are tides predicted?

Tides are arithmetic on the motions of the moon and the sun, so they can be predicted years ahead. Each station has a table for every month from a year back to two years ahead.

What is a king tide?

The highest predicted tides of the year, when a spring tide coincides with the moon at its nearest to the earth. Where NOAA has set a coastal flood level, a station page says when the tide alone is predicted to reach it.

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