High Tide Flooding Outlook for May 2026

High Tide Flooding Outlook for May 2026 © US Harbors

The arrival of a new boating season for much of the country means that anything is possible on the coast — including the chances of high tide flooding.

Sea levels in regions such as the Northeast and Mid-Atlantic are typically higher in the late spring, largely due to changing weather patterns and warming water temperatures. As a result, many locations will see their highest water levels of the year in May, with nearly two dozen significant East Coast ports including Boston, Cape May, and Cape Canaveral all predicted to have possible flooding. The West Coast and Hawaiian Islands will also see the possibility of flooding in many harbors, with high-water events likely on the Big Island. Higher than normal high tides will occur around the new moon, on May 16, and on the two full moons that occur this month — on May 1 and May 31. These higher than normal tides (and lower than normal lows) occur during the perigean spring tide, when the moon is new and closest to Earth. If a storm happens to occur during these periods, the potential for coastal flooding and erosion will increase even more.

Note that a harbor's absence from this list, despite it being in proximity to a harbor that is (for example: Montauk, New York, and Woods Hole, Massachusetts, both of which are near harbors that are listed as seeing possible flooding, don't make the list themselves), does not mean that flooding is not possible. Instead, it simply means that NOAA either does not have a sufficiently validated model to make an accurate prediction, or that the local hydrodynamics makes such a prediction impossible.

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