A tide chart helps you read a prediction of water level at a particular station. It does not tell you whether a beach is safe, how deep the water is beneath a boat, or how strong a current will be.
Learning to read one starts with its settings, not just the next low tide. This beginner’s guide explains what to check, how to interpret a table or curve, and where the information stops being enough.
1. Check the station and date
Start with an official prediction source. NOAA’s Tide Predictions help page explains its station-based interface and display settings.
Confirm the station name and the dates shown. A station prediction belongs to that location; a familiar town name or a nearby dot on a map does not automatically make the information suitable for another beach, inlet, or harbor. Use site-specific official guidance to establish which source applies to your intended location rather than guessing.
For practice, you can read a station’s prediction at home without making any outing decisions.
2. Read the clock settings
Do not assume that every chart shows local clock time. NOAA’s interface offers several time-zone settings:
- LST/LDT: local time with daylight-saving adjustment as appropriate.
- LST: local standard time, without daylight-saving adjustment.
- GMT: Greenwich Mean Time.
The display can also use a 12-hour or 24-hour clock. With a 12-hour clock, check AM and PM. With a 24-hour clock, 14:30 means 2:30 PM in the selected time zone, not necessarily in your own.
Record the time-zone setting beside any times you copy. A screenshot without its settings can be misleading.
3. Check the units and reference level
The height may be in feet or meters. It is measured relative to a stated reference level, called a datum, rather than from the seabed directly below the water.
One tidal datum you may see is Mean Lower Low Water, or MLLW. NOAA defines it as the average of the lower low water height of each tidal day over the relevant National Tidal Datum Epoch. It is a reference derived from observations, not a guarantee that the water cannot fall below it.
A negative predicted height means below the selected datum. It does not mean “negative water depth,” nor does a positive value tell you the depth at your feet. Do not combine heights from different reference levels as though they use the same zero.
See NOAA’s datum definitions for the reference terms used in its products.
4. Find the high and low predictions
In a high/low table, match each event with its date, time, predicted height, and high-or-low label. On a prediction curve, time runs along the horizontal axis and water level along the vertical axis. Peaks represent predicted high waters and troughs predicted low waters over the displayed period.
Do not assume each calendar date contains an identical pattern. NOAA explains that tidal patterns differ: some locations have one high and one low tide per day, while many have two of each, often with unequal heights. Read the events actually listed rather than filling in an expected schedule.
NOAA’s explanation of daily high tides describes these different patterns.
5. Practice with a fictional example
The following entries are invented solely to practice reading labels. They are not predictions for any place or date and must not be used to plan a visit.
| Event | Displayed time | Predicted height |
|---|---|---|
| Low water | 08:00 | −0.2 feet |
| High water | 14:30 | 4.1 feet |
For this exercise, assume a 24-hour clock, LST/LDT, and an MLLW datum. The first entry means a predicted water level 0.2 feet below that reference level at 8:00 AM in the selected local time. The second means 4.1 feet above the same reference at 2:30 PM.
Neither entry gives water depth, wave height, current speed, or permission to walk onto exposed rocks. The table also does not show what happens before or after these two events.
6. Keep tides and currents separate
Tides describe the rise and fall of water level. Currents describe water moving horizontally. Related does not mean interchangeable.
Do not use a high- or low-water entry as a current-speed forecast, or assume it identifies a safe crossing or swimming window. Activities that require current information need the appropriate separate local current predictions and qualified guidance.
NOAA’s tides and currents explanation introduces the distinction. This article is not navigation, boating, or ocean-swimming instruction.
7. Remember that a prediction is not the whole beach
NOAA’s Tides and Currents FAQs explain that prediction accuracy varies by location and that astronomical tide predictions have limits. Do not treat the curve as a complete forecast of conditions.
Before an outing, separately check current official weather and beach-hazard information, closures, water-quality notices where relevant, and site rules. Follow lifeguard and site-staff instructions. Low tide is not a general assurance of safe access, and there is no universally best tide for surfing, fishing, or exploring a shore.
For help keeping a plan adaptable, read How Coastal Weather Teaches Flexibility and Preparedness. If you are hoping to observe wildlife, How to Observe Marine Life Without Disturbing It keeps the focus on permitted places and avoiding disturbance.
A simple at-home check
Open an official station prediction and write down five things: station, date, time-zone setting, height units, and datum. Then find one listed high or low event and explain what its time and height mean using those settings.
Children who enjoy comparing numbers can help spot labels with an adult. Younger children might draw an imaginary rising and falling line, clearly marked as a drawing rather than real data. No beach visit or purchase is needed.
The useful skill is not memorizing a pattern. It is knowing what the prediction says, what it does not say, and which questions still need current local answers.
Sources were reviewed through official NOAA search extracts and are linked above. The featured coastal-notebook watercolor is illustrative, not a tide chart, station photograph, or navigation aid.
