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Guide

Reading a tide table on the Gulf

Checked September 28, 2026 against NOAA Tides and Currents, NOAA’s National Ocean Service, the Conrad Blucher Institute at Texas A&M University–Corpus Christi and TxDOT’s Hydraulic Design Manual.

The Tides tile repeats NOAA’s predictions for the station nearest your town and, where there is one, what its gauge is measuring now. On this coast the tide is small, and the wind can move the water more than the Moon does. This page explains what the zero is, the shape of the Gulf’s tide, which stations are measured, and how to read the gap between the prediction and the water.

Zero is not the bottom

Every height on the tile is measured from mean lower low water — MLLW — which NOAA defines as “the average of the lower low water height of each tidal day”, taken over the National Tidal Datum Epoch. Because it is an average, many low tides fall below it: a prediction of −0.3 ft is not an error. A charted depth is also measured from MLLW, so a channel charted at 4 feet has less than that on a minus tide.

A small tide, often once a day

NOAA’s National Ocean Service gives the Gulf as an example of an area with “only one high and one low tide each day”: a diurnal tide. TxDOT’s coastal design manual puts the Texas coast the same way, adding that “there are times each month where semi-diurnal tides occur”. So most days the table shows one high and one low, and on some days two small highs and two small lows. Neither is a mistake.

The range is small. TxDOT says the average daily range along the coast is “less than 2 feet”. NOAA’s own figure for each station is the great diurnal range, the difference between mean higher high water and mean lower low water:

StationRangeGauge
Port Isabel 87797701.37 ftLive
South Padre Island CG Station 87797481.37 ftLive
Bob Hall Pier, Corpus Christi 87758701.64 ftPredictions only
USS Lexington, Corpus Christi Bay 87752960.61 ftLive
Port Aransas 87752371.04 ftLive
Rockport 87747700.36 ftLive
Port O’Connor 87737010.72 ftLive
Galveston Pier 21 87714501.41 ftLive
Clear Lake 8770933—Predictions only
Morgans Point, Barbours Cut 87706131.33 ftLive
Port Arthur 87704751.04 ftLive
Sabine Pass 87705701.60 ftPredictions only

These are some of the stations the boards read, not all of them: the Lower Laguna Madre board reads three stations, the Coastal Bend board twelve stations and the upper coast board sixteen stations, and each town’s own is on its tile. “Live” means NOAA publishes the gauge’s measured level as it comes in; “predictions only” means a table and nothing measured. A dash means NOAA publishes no datum figure for it.

Inside the passes there is even less

Compare Bob Hall Pier on the Gulf beach, 1.64 feet, with the USS Lexington in Corpus Christi Bay, 0.61, and Rockport, about a third of a foot. The bays behind the barrier islands get much less tide than the beach; TxDOT names the USS Lexington as a place where the tidal signal is damped.

In the Laguna Madre it nearly disappears. NOAA classes its gauges at Port Mansfield, Baffin Bay, South Bird Island and Rincon del San Jose as non-tidal and publishes no tide predictions for them. So Loyola Beach, on Baffin Bay, reads Packery Channel, the nearest prediction NOAA publishes, thirty-six miles away at the pass into the upper Laguna; its tile says how far, and in Baffin Bay itself the wind decides the water, not the table. Palacios reads Port O’Connor, twenty miles down Matagorda Bay, because there is no prediction on Tres Palacios Bay.

Who runs the gauges

Many of the gauges on this coast belong to the Texas Coastal Ocean Observation Network (TCOON), which the Conrad Blucher Institute at Texas A&M University–Corpus Christi has maintained for more than three decades. The State of Texas established it in 1991, and it is a cooperative effort of the General Land Office, the university, NOAA, the U.S. Army Corps of Engineers and the Texas Water Development Board. Its data appear on NOAA’s Tides and Currents site. Of the live stations above, South Padre Island CG Station, the USS Lexington, Port Aransas, Morgans Point and Port Arthur carry NOAA’s TCOON note, which cautions users before relying on the data for “critical decisions such as those that concern physical or public safety.”

Why the water is not where the prediction said

NOAA is direct about what a tide table leaves out:

“We can only predict the astronomical tides” — the pull of the Moon and Sun.

It “cannot predict the effect that wind, rain, freshwater runoff” and other short-term weather will have on them.

On a coast with a one-foot tide, those effects can be bigger than the tide. The National Ocean Service: “Onshore winds may act to pile up water onto the shoreline”, and strong offshore winds “move water away from coastlines”. This coast faces the Gulf to the east and southeast, so a steady southeast wind is onshore and holds the water up, and the north wind behind a front is offshore and pulls it down. TxDOT adds that onshore wind or a storm “elevates tides above predicted levels”.

How big: between October 1, 2025 and September 27, 2026, NOAA’s hourly heights at Galveston Pier 21 ran as much as 2.6 feet above the prediction and 2.0 feet below it — against a daily range of 1.4. At Rockport, whose range is about a third of a foot, the water ran as much as 1.5 feet above.

So read the tile this way. Where the station has a live gauge, the measured level is the answer and the prediction is a guide to when it will rise and fall. Where it has predictions only, treat the table as the start of the question and look at the wind forecast. And a hurricane’s storm surge is a different thing altogether; it is the weather service’s warnings, not the tide table, that speak to it.

Sources