How we calculate
80 places, predictions 30 days ahead
Source
All tide times and heights are predictions published by NOAA's Center for Operational Oceanographic Products and Services (CO-OPS) through its public data API. NOAA data is in the public domain; we credit NOAA on every page. We download high and low tide predictions every day for the next 30 days.
Which station belongs to a place
For each beach or town we use the NOAA prediction station that carries its name or, where no station does, the nearest station on the open coast. The station number, its name and – where relevant – the distance are shown on every page. Subordinate stations (type S) are derived by NOAA from a nearby reference station with time and height corrections.
Heights and times
Heights are in feet above mean lower low water (MLLW), the datum used on U.S. nautical charts. Times are local time at the station including daylight saving time.
The tide curve
NOAA publishes the times and heights of high and low tides. Between them we draw the curve with the common cosine approximation. The dots on the chart are NOAA's values; the line in between is our interpolation.
Sunrise and sunset
Calculated for the station's coordinates with the suncalc library (formulas after Jean Meeus).
Not for navigation
Predictions describe the astronomical tide. Wind, storms, air pressure and river flow change the real water level. For boating and safety decisions use official NOAA products and observations.