Based on recent data, the high tide in St Ives can reach around 6.5 meters during spring tides, as indicated by Cornish weather reports. Tidal heights vary daily, with spring tides often producing the highest levels, while neap tides are lower.
It was here at Burntcoat Head that the highest tides ever at 53.6 feet were recorded on the Bay of Fundy. The Guinness Book World Records declared in 1975 that this unique place on the bay has the highest tidal range in the world. The range at high tide swings between 47.5 and 53.6 feet.
The king tides occur at new and full moon when the Earth, Moon and Sun are aligned at perigee and perihelion, resulting in the largest tidal range seen over the course of a year. So, tides are enhanced when the Earth is closest to the Sun around January 2 of each year.
King Tides are the highest high tides of the year—one to two feet higher than average high tides, which is a good approximation of how high we expect everyday tides to be over the next few decades due to human-caused sea level rise.
The 50/90 rule (or 50/90/100 rule) is a simple guideline for estimating tidal current speed, stating that an hour after slack water (0% flow), the current reaches 50% of its max speed, then 90% by the second hour, and 100% (maximum) at the third hour, before slowing back down in the same pattern (90%, 50%) until the next slack water in the sixth hour, indicating a cycle of roughly 0/50/90/100/90/50/0% flow over six hours. It's a useful rule of thumb for kayakers and sailors for basic planning, though it's less accurate in complex areas like estuaries compared to official charts.
The immense tidal range of the Severn Estuary and its coastal geometry combine to build up the largest tidal bore in the UK further up the estuary. It boasts the second highest tidal range in the world, between 12 and 14m, which is second only to the Bay of Fundy in Canada.
The Severn Estuary is the second largest estuary in Britain and boasts the highest tidal range in Europe. At the Bristol Channel, water depth ranges from 50m at its seaward end to 10m near Avonmouth, where it then gradually shallows.
An efficient way of guesstimating how much water there is, at any given time of day, over a particular point. The rule of twelfths works like this; take the difference in height between the high and low tide on that day, and divide that by 12 equal chunks.
The difference between high and low tide on a day is described as the range. In Falmouth e.g., the range of the tides can vary between 7.5 ft in Neaps and almost 16 ft in Springs. It is important to know the Cornwall Tide times especially if you are planning to get involved in an activity near or on the water.
Bay of Fundy, New Brunswick, Canada. At the pinnacle of tidal extremes is the Bay of Fundy, located between New Brunswick and Nova Scotia in Canada. ...
Ungava Bay, Canada. Not far behind is Ungava Bay in northern Quebec, Canada. ...
King tides generally happen twice a year. They happen at different times throughout the world because each location lines up with the sun and moon just right at different times. King tides are rare, but predictable! Next time there's a king tide, put it on your calendar and plan a trip to the shore.
Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas experience two high and two low tides every 24 hours and 50 minutes. High tides occur 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the water at the shore to go from high to low, or from low to high.
The king tides occur when the earth, moon and sun are aligned at perigee and perihelion, resulting in the largest tidal range seen over the course of a year. Alignments that are 'near enough' occur during approximately three months each winter and again for three months in the summer.
What time of year are the highest tides in the UK?
The highest tides of the year in the UK, known as spring tides, occur around the equinoxes (March/September) when the Sun, Moon, and Earth align, creating the largest tidal range, especially in the Bristol Channel/Severn Estuary, which boasts the UK's largest range (up to 15m), second only to Canada's Bay of Fundy globally. While specific dates vary yearly, the highest predicted astronomical tides for 2025/2026 were in late 2025 and early 2026, with dates like November 7, 2025, and March 21, 2026, seeing heights over 13m at some locations.
WHAT IS A KING TIDE? The king tide is the highest predicted high tide of the year at a coastal location. It is above the highest water level reached at high tide on an average day. WHEN IS A KING TIDE? King tides are a normal occurrence once or twice every year in coastal areas.
The Severn Estuary has an astonishingly high tidal range of 15m - which is off the upper end of the scale on the map above by a factor of more than 10. In fact, it is the second largest tidal range in the world, just behind Canada's Bay of Fundy with 16.3m.
Because the UK is surrounded by water which is constricted somehow, either by other landmasses (Ireland, mainland Europe) or by depth. As the moon drags water around, it gets blocked by these landmasses and therefore has no way to go except up (making the tide higher).
