Moon and sun pull together, then against each other
The tides are caused by the gravitational pull of the moon and the sun. According to the German Federal Maritime and Hydrographic Agency (BSH), which tidal effects occur depends on the positions of earth, moon and sun relative to each other and on the rotation of the earth.
When sun, earth and moon are roughly in line, at full and new moon, the forces reinforce each other. When sun and moon are at right angles, at the first and last quarter, they partly cancel each other out. This creates the half-monthly inequality: high and low tides vary in a rhythm of about two weeks.
Spring period, neap period and the days between
For the German North Sea coast the BSH defines the terms simply: the spring period covers the four days from the day of full or new moon, the neap period the four days from the day of half moon. The days in between are called the middle period.
There is a reason why the spring period only starts with full or new moon and lasts several days: the highest high tide arrives on the coast with a delay after the moon phase. The BSH calls this average delay the spring delay, and its counterpart at neap tide the neap delay.
What you notice on the beach
At spring tide, high tide rises higher and low tide falls lower, so the difference between them is larger. At neap tide the difference is smaller. Around the spring period, larger areas of mudflat are therefore often exposed at low tide, and the water comes further up the beach at high tide.
If a spring tide coincides with strong onshore wind, the water level can rise further. That is a situation in which you should pay particular attention to the official BSH water level forecast. On the tide map you see the water level model, which includes weather effects, next to the calculated tide.
Spring tide does not mean danger, but higher high tides and lower low tides. Around full and new moon, check the times and heights for your place, especially in strong wind.
See the tide for your placeFrequently asked questions
Is a spring tide the same as a storm surge?
No. The spring tide is a regular astronomical phenomenon. A storm surge is caused by wind and weather; on the North Sea the BSH speaks of a storm surge from 1.5 metres above mean high water.
How often is there a spring tide?
About every two weeks, after each full and new moon. In between lies the neap period after half moon.
Does spring tide have anything to do with the season?
No. The spring period follows the moon phases, not the season. It occurs all year round after every full and new moon.