The tide is a wave going around Ireland
The pull of the moon and sun builds the tide in the open Atlantic, and it arrives at Ireland as a very long, very low wave, hundreds of kilometres from crest to crest. It hits the west coast first. Galway, Kerry, Clare and Mayo have their high water within about an hour and a quarter of one another.
To reach the east coast it has to go around: north past Malin Head and in through the North Channel, and south past Cork and in through St George’s Channel. Comparing the Marine Institute predictions this autumn, high water in Dublin comes roughly six hours apart from high water in Galway. In practice the two coasts run nearly opposite: a morning high in Salthill is a morning low on Sandymount strand.
Where the tide almost disappears
The two branches meet in the Irish Sea and, off the Wicklow and Wexford coast, largely cancel. Our data shows it clearly. The typical range is 2.7 m at Dublin Port, 1.8 m at Wicklow, 0.6 m at Arklow and about 1 m at Wexford and Rosslare, before it climbs again along the south coast to around 2.8 m at Dunmore East.
Where the range is that small, the tide curve is flat and its shape is lopsided, so the moment of “high water” is less sharp. Dublin Port’s own tables put Arklow 2 hours 43 minutes ahead of Dublin, while Wicklow, only 25 km further north, is just 18 minutes ahead. If you fish or launch on that stretch, look at the heights through the day rather than the single high water time.
Bays and estuaries run late
A tide entering a long bay or river has to push water up a narrowing, shallowing channel, and it slows down. The Shannon shows it well: high water at Kilrush is about 25 minutes after Carrigaholt at the mouth. Wexford Harbour, behind its sand bar, has high water about 40 minutes after Rosslare and low water well over an hour later, because the harbour takes a long time to drain through the narrow mouth.
That is why each beach page on this site says which gauge it borrows from and how far away it is. On an open coast a gauge 10 km away is usually within a few minutes. At the head of a bay, behind a bar or up a river, allow 10 to 30 minutes later, and expect low water to lag more than high water.
Two Dublin gauges, two answers
Dublin has gauges at Dublin Port, Howth and Tom Clarke Bridge on the Liffey. Howth is about five minutes ahead of the port, the river gauge within a few minutes behind it. Small differences, but they are why we keep separate pages: the bay beaches use the port, the city quays use the river, the north side of the bay uses Howth. The Co. Dublin page puts them side by side.
Weather: the part no table can predict
Every tide table in Ireland, ours included, is an astronomical prediction. The Marine Institute says plainly that storm surge from air pressure and wind is not included. Two effects matter:
- Air pressure. The sea rises about 1 cm for every hectopascal below normal pressure (about 1013 hPa). A deep Atlantic low at 980 hPa lifts the sea by about 30 cm.
- Wind. A strong onshore wind piles water against the coast, and in a shallow bay like Dublin or Dundalk that can add tens of centimetres more. An offshore wind does the opposite and can leave low water lower than predicted.
On their own, spring tides near the March and September equinoxes are harmless. When one of them meets a deep low and an onshore gale, the combination floods coastal roads, car parks and low-lying homes. Met Éireann issues coastal warnings for exactly that. In a storm, treat the predicted high water as the least you will get.
Small print: how close are the predictions?
In settled weather, very close. We compared our Dublin predictions with Dublin Port Company’s published table for 1 November 2026: times within 1 to 10 minutes and heights matching to within a few centimetres once the datum is converted. The gap comes from different gauge positions and prediction methods, not errors. The datum guide shows the comparison.