2018 State of U.S. High Tide Flooding with a 2019 Outlook

NOAA's fifth annual update of the State of Coastal High Tide Flooding (HTF) provides HTF projections to inform adaptation and decision-making for the following year, and over the longer term. High tide flooding (aka ‘sunny day’ or ‘nuisance’ flooding) occurs when water levels measured at NOAA tide gauges exceed heights based on the minor-flood thresholds set by NOAA’s National Weather Service. This report updates high tide flood frequencies during 2018 (based on the meteorological year: May 2018-April 2019) at 98 NOAA tide gauge locations, and provides a statistical outlook for 2019 (May 2019 - April 2020). Communities can use this information to estimate their risk of coastal flooding, and to help build resiliency into planning for the long-term impacts of sea level rise.

High tide flooding frequency in 2018 tied the historical record set in 2015 at 5 days (median value). Regionally, HTF in 2018 was most prevalent along the Northeast Atlantic Coast, Chesapeake Bay, and the Eastern Gulf of Mexico Coast. 42 locations are experiencing significant acceleration (nonlinear increases) of HTF trends, threatening to become a chronic problem without adaptation.

Because high tide or sunny day flooding is disruptive and damaging to coastal communities impacting storm/waste/fresh water systems, roads, harbor operations, and first floor businesses and residences, ‘next year’ and long-term projections are important for preparedness and adaptation planning.  Nationally, HTF frequency is projected to be more than 100% greater than in 2000, with the Southeast expected to experience the greatest increase of 190% since 2000. Long-term projections place the national HTF frequency at 7-15 days by 2030, and 25-75 days by 2050. 


Publication Date: June 2019

Authors or Affiliated Users:

  • William Sweet
  • Greg Dusek
  • Doug Marcy
  • Greg Carbin
  • John Marra

Related Organizations:


Resource Category:

Resource Types:

  • Climate science
  • Monitoring


Go To Resource