Fast Facts / High Tide Flooding

High Tide Flooding

High tide flooding, sometimes referred to as nuisance flooding, sunny-day flooding, or king tide flooding, is occurring more frequently every year as sea levels continue to rise, and is increasingly disrupting coastal community life.

400 to 1,100% Increase

The U.S. Southeast Atlantic and Gulf Coast regions saw an increase of over 400 to 1,100 percent, respectively, in high tide flooding days compared to the year 2000.

Twice as Frequent

The U.S. annual high tide flooding frequency is more than twice that in the year 2000 due to rising relative sea levels. By 2030, the national median frequency rate is likely to increase by two to three times (seven to 15 days).

Up to 85 Days per Year

By 2050, high tide flooding is likely to occur between 45 and 85 days per year, depending on location.

Rapid Growth, Record-Breaking Rise

Assessed over several decades, the national trend in high tide flooding frequency is accelerating, and is more than twice as likely now as it was in 2000. The rapid growth is in response to relative sea level rise, which is occurring along most U.S. coastlines and around the globe. In 2023, global average sea level set a new record high: 101.4 millimeters (3.99 inches) above 1993 levels. Global mean sea level has risen about eight to nine inches (21 to 24 centimeters) since 1880.

Annual Acceleration

The national annual high tide flooding frequency reached four days on average in 2022, equaling the previous year and just shy of the record of five days set in 2018. High tide flooding is now rising and/or accelerating at nearly all NOAA tide gauge locations.

Vulnerable Coastlines

Compared to high tide flooding frequencies typical in 2000, 2020 was extraordinary. Flood days occurred 100 to 150 percent more frequently than in 2000 along the Northeast Atlantic and Eastern Gulf coastlines. Even higher percentage increases (more than 400 percent) occurred along the Southeast Atlantic (for example, more than a 400 percent increase in Charleston, South Carolina, with 14 days in 2020, compared to about two days in 2000). Percentage increases compared to 2000 were the greatest in the Western Gulf (more than 1,100 percent, or 22 days) in Bay Waveland, Mississippi.

In 2022, the Mid-Atlantic region experienced the most flood days–eight on average. However, the location with the highest number in the nation was Bar Harbor, Maine, at 16 days.