Simple Tides / Guides / Tide Tables vs. Real-Time

Tide Tables vs. Real-Time Water Levels: What's the Difference

A printed tide table and a live water-level gauge can disagree, and knowing why helps you trust the right one at the right moment.

Tide tables are predictions

A tide table (or the tide chart on a prediction-only station) is calculated in advance using harmonic analysis: years of historical water-level data broken down into the underlying tidal patterns caused by the sun and moon, projected forward. They're published well ahead of time and don't account for that specific day's weather.

Real-time water levels are measurements

A real-time or "water levels" station reports what a physical gauge is actually reading right now. This reflects everything happening that day — predicted tide, plus wind setup or setdown, storm surge, unusual river flow, or atmospheric pressure effects — not just the astronomical prediction. See our full breakdown of NOAA station types.

When they disagree

Under calm, typical conditions, the two generally track closely. During storms, strong sustained wind, or unusual freshwater runoff, real-time readings can run noticeably higher or lower than the predicted table — sometimes by a foot or more. This is exactly the scenario where you want the live gauge over the printed prediction.

Which one to trust for planning

For routine trip planning days or weeks out, the predicted tide table is the practical choice, since a live reading doesn't exist yet for the future. For same-day decisions, especially in unusual weather, check a real-time water-level station near you if one exists, and treat a big gap between the prediction and the live reading as a signal that conditions are running abnormal.