What are "king tides" and when do they occur?
The "king tides" are higher-than-usual tides which typically occur in Florida in the fall, and which can produce local "sunny day" flooding, or flooding which occurs even though there is no rain. The National Oceanic and Atmospheric Administration (NOAA) publishes predictions of high tide heights for their Lake Worth tide gauge here, which can be used to anticipate days on which king tides may occur. NOAA also recommends sea levels at which scientists should be on the alert for potential flooding, called the action stage, and at which they think flooding will occur, called the flood stage. Because so many things, like weather, can influence the height of the tide from day to day, and because your particular location may flood below NOAA's official flood stage, we like to be aware of any high tide which is predicted to come within three inches of the action level, just in case!
Days when we expect the highest tides in 2021 are:
- October 7–10, expected within three inches of action stage
- November 3–4, expected within three inches of action stage
- November 5–7, expected to exceed action stage but not reach flood stage
- November 8, expected within three inches of action stage
- December 3–6, expected within three inches of action stage
Please note that king tides for 2021 are not predicted to reach flood stage, but that various factors, including storms, may cause higher-than-expected sea levels and flooding, and that your location may flood at lower sea levels than the NOAA action stage or flood stage. King tide flooding is not guaranteed during these dates, and sunny-day and other types of flooding, such as rainfall-induced flooding, may occur outside of these dates!
Why do king tides occur?
Before diving into king tides, it's first important to understand how tides work.
This site does a great job of explaining what causes tides; simply put, tides occur as a result of the moon's gravitational pull on our oceans. The height of tides depend mostly on where the moon is in its 28-day orbit around the Earth and on every 14th day, the moon and the sun line up with the Earth, creating a spring tide. Despite the name, spring tides occur every two weeks, year round, and coincide with the full moon or a new moon! Some spring tides are higher than others based on how close the moon is to the Earth at that time.
A "king tide" is a non-scientific term used to explain exceptionally high spring tides. In Florida, king tides are generally
experienced in the fall, when seasonal factors like currents and
temperature bring sea levels to their highest for the year. The exact
timing of the highest tide is influenced by local factors such as water
temperatures, rainfall, storms, and variations in ocean currents.
In some years, king tides can be even higher than usual when they coincide with higher-than-usual tides called
perigean spring tides. They occur during a new or full moon when the moon is in alignment with the sun AND in its closest point in orbit to the Earth (perigee), resulting in the greatest gravitational pull. You can explore
the National Oceanic and Atmospheric Administration (NOAA) infographic below to better understand how perigean spring tides work.
NOAA High Tide Flooding Infographic - Click to enlarge image.
In low-lying areas, king tides can result in minor flooding. This flooding, which can lead to road closures, overwhelmed storm drains, and compromised infrastructure, is commonly called
According to NOAA, on average, nuisance flooding has increased about 50 percent in the last 20 years.
Major coastal flooding can occur when king tides occur simultaneously with strong onshore winds and barometric pressure changes from a coastal storm, or with perigean spring tides. Coupled with sea level rise, both minor and major coastal flood risks are expected to increase.
What can you do to adapt to nuisance flooding?
Currently, most king tide impacts are experienced by coastal property owners and those living in very low-lying areas near other water bodies. To study the elevation of your home, or see how sea level rise may affect your home, you can check out any of the interactive mapping resources located on our Mapping Tools webpage. With one such tool, National Oceanic and Atmospheric Administration’s Sea Level Rise Viewer, you can zoom into your neighborhood, click the “High Tide Flooding" tab, and see areas in red that are vulnerable to King Tide flooding.
To PREPARE for a king tide, please consider the following options:
- Have a plan in-place to move your vehicles to higher ground BEFORE a king tide event
- Keep sandbags on-hand
- Consider obtaining an elevation certificate from a licensed surveyor
- Review your flood insurance policy, or consider acquiring flood insurance
- Make a flood safety plan, and review it with your family/friends/co-workers
- Study the elevation of the areas around your property and identify alternative routes to avoid driving through floods in the case of a king tide event
- Remove waste carts and recycling bins from the curb as soon as possible when you are expecting a king tide event
To PROTECT yourself and your loved ones during or after a king tide, please:
- Do not walk through flood water if possible. This can be a health and/or safety issue
- If you do need to walk through flooded waters, practice good hygiene and wash your hands, clothes, and pets as soon as possible
- Do not drive through flood waters if possible. This can be dangerous to you, and can damage your vehicle
- Be aware of the new tidal range, and practice safe boating when traveling under a bridge. Check the tides before leaving the dock.
- During king tide events, closely monitor your waste carts and recycling bins, and remove them from the curb as soon as possible as soon as they are emptied. If your property experiences flooding, consider storing your containers in a secure location until the next scheduled pick-up day.