About the tide data

Every tide time and height on this site comes from the tide predictions of NOAA's Center for Operational Oceanographic Products and Services (CO-OPS), a U.S. government source in the public domain. We download 8 days of high and low tide predictions for each station every day and publish them as they are.

Sun and moon. Sunrise, sunset, moonrise and moonset are computed for each station's coordinates with the PyEphem astronomy library, using the U.S. Naval Observatory conventions (upper edge of the disk, standard refraction), and agree with independent JPL ephemeris calculations to within a couple of minutes. Solunar periods follow the traditional rule: two-hour major periods around the moon's upper and lower transit, one-hour minor periods around moonrise and moonset. They are a fishing tradition, not a scientific forecast.

Predictions, not observations. Strong wind, low or high air pressure and river flow can move the real water level by a foot or more. For navigation use official charts and NOAA's real-time water levels.

Heights are in feet above mean lower low water (MLLW), the average of the lower of the two daily low tides, which is the zero on U.S. nautical charts. Times are local, with daylight saving time where it applies.

Subordinate stations have no gauge of their own: NOAA computes their tides from a nearby reference station with time and height corrections.

We are not affiliated with NOAA.