On the basis of the sea water level observations made, the warning limits have been set so that the frequency of warnings at the lowest risk level is once a year, at the second risk level once in five years, and at the highest risk level once in 20 years.
Only one warning level is used for low water (yellow), but all three warning levels are used for high water (yellow, orange and red).
Warnings for sea level are drawn up for periods of up to 5 days.
The warning limits are listed in the table below:
|low water||high water||very high water||dangerously high water|
|once a year||once a year||once in five years||once in 20 years|
|Northern Bay of Bothnia||-80||115||140||170|
|Southern Bay of Bothnia||-65||85||110||130|
|The Quark (Vaasa)||-50||85||110||130|
|Sea of Bothnia||-50||75||100||120|
|Sea of Åland and Archipelago (Föglö)||-50||65||85||100|
|Sea of Archipelago (Turku), Western Gulf of Finland (Hanko)||-50||70||95||110|
|Western Gulf of Finland (Helsinki, Porvoo)||-60||80||115||130|
|Eastern Gulf of Finland||-70||110||145||170|