King Tides vs Large Waves

Time to clear up some confusion about King Tides. Many people think they’re about big waves, but that’s not quite right.

This post was created in partnership with the Oregon Coast Visitors Association Coast Like a Local campaign.

While I’ve done some blogs about King Tides already and how to read a tide chart (see here), I’ve been asked recently by some partnering Destination Management Organizations to make some content helping visitors understand the difference between king tides and big waves. We’ve seen many questions or statements about King Tides recently that make us realize many people have a wrong idea about what they are.

While King Tides happen in the winter which is also when we get our biggest storms, these two very different factors can combine to create dramatic coastal conditions. But King Tides and big waves do not always line up, meaning sometimes King Tides are high water levels with very little wave action.

So what’s the difference?

King Tides

King tides are the highest predictable tides of the year, occurring when the gravitational pull of the moon and sun aligns with the Earth’s orbit being closer to the sun, causing water levels along the shoreline to rise higher than normal. These tides are essentially water heights and are cyclical and predictable far in advance, but don’t have anything to do with big waves.

See here for how tides are predicted and how to read a tide chart.

Big Swells/Waves

Big swells, on the other hand, are the height of the waves themselves and are influenced by wind strength, direction and duration. Storms far out at sea can generate long-period swells that travel hundreds of miles, creating powerful, crashing waves when they reach the coast. Unlike tides, which are predictable far in advance, swell heights can vary daily depending on weather systems, storm intensity, and wind direction and require you to check surf reports closer to a specific date of interest.

How to read a swell chart:

Start by looking at websites and apps that track ocean conditions and marine forecasts. There are so many options of apps and websites to use, but generally I use Windy and Surfline. You can look at these on your desktop or download the apps to your phone. I tend to look at these apps about a week out from when I’m curious about ocean conditions. Keep in mind conditions can change from day to day so checking before hand and then on the day you’re headed out are both recommended.

For either app, their forecasts should include things like wave height (ft), swell period (s), and wind strength (kts) and direction. If looking for big waves, wave height is really the main thing you’ll be paying attention to, but depending on how much into the nit and gritty you want to get, swell period, as well as wind and swell direction will also play into specific conditions.

Wave height is going to tell you just that, the predicted height of the waves. Simply put, the bigger the wave height, the bigger and potentially more exciting the ocean may appear. In summer months along the Oregon Coast, this is sometimes as small as 1-2ft, while in the winter, bigger swells (10-20ft) are more consistent. The highest I have ever seen a surf report in Oregon was 30-40ft in December!

Getting into other more specific factors, the swell period is the time, in seconds, between the crests (top of the waves) of successive waves. Longer swell periods (12–20+ seconds) mean the waves have traveled farther and have more energy, often creating bigger and more powerful waves when they break at the shore. Shorter periods (under 10 seconds) produce lower energy waves that can be choppier and less organized.

Swell direction refers to the angle from which the swell is approaching the coast. Waves break differently depending on the shoreline orientation and underwater topography. A swell coming directly onto the beach typically produces strong, plunging waves, while a swell approaching at an angle can create peeling waves that look cleaner or break unevenly along the shoreline.

Together, swell period and direction help determine wave size, shape, and power.

How does wind play into all this? Offshore winds, or winds blowing from land toward the ocean, tend to groom waves, holding them up and making them cleaner and steeper. Onshore winds, or winds blowing from the ocean toward the land, push against the incoming swell, often creating choppy, messy waves that break unpredictably. Even a strong swell with a long period and ideal direction can be disrupted by unfavorable winds, so the combination of swell period, swell direction, and wind direction all work together to determine the size, shape, and power of waves along the shore. Understanding these factors is crucial for predicting wave conditions, whether for surfing, photography, or safe coastal observation.

Of course when looking for big waves, it’s also smart to monitor tide charts, since high tide combined with big swells can create dramatically larger waves and more hazardous shorelines (sometimes there’s no beach at all!!).

In short: king tides determine how high the water sits along the shore, while big swells determine how large and powerful the waves are, two separate factors. Tides are predictable years in advance while swells are more variable and require looking at swell forecasts.

To see when king tides are, check tide charts.

To see when big waves are, check surf reports.

Again, since King Tides happen in the winter (when earth is closest to the sun so the gravitation pull is stronger) which is also when we get our biggest storms, they can of course combine to create dramatic coastal conditions. That being said, sometimes King Tides are high water levels with very little wave action. I’ve heard people refer to King Tides as “boring” when this happens, but remember King Tides have nothing to do with the size of waves!

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If you do visit during a King Tide, there’s a great opportunity to contribute to an ongoing citizen science project: the Oregon King Tides Project.

Understanding and documenting the extent and impacts of especially high tide events is one way to highlight the need to prepare for the effects of future climate conditions. The King Tides Project generates information that coastal communities can use to reduce vulnerabilities to rising sea levels.

So bring your camera, and enter the photo contest by submitting side by side photos that highlight the difference between regular and king tides. The contest will be open through February, with prizes given in 4 categories: Bays + Estuaries, Waves + Erosion, Coastal Flooding, and Youth Photography (under 18 w/ guardians’ permission).

Once you’re out there, please be safe! See Oregon Coast Visitors Association Coast Like a Local on beach safety.

• Know before you go! Check weather patterns, tide schedules, and fire restrictions.

• Sign up for emergency alerts from OR-Alert.

• Exercise common sense and caution during stormy weather, and to consider staying home on more risky, stormy days.

• A good rule that locals like to follow: Never turn your back to the ocean. Sneaker waves are real! These forceful waves are sudden (it’s right there in the name) and are known for carrying anything in their path out to sea.

• Don’t swim alone! Look out for signs of rip currents, which can be unpredictable and powerful. It’s also helpful to know the tidal predictions for that day.

• Take the time to carefully navigate rough and slippery coastal terrain, and refrain from climbing on driftwood logs, rocks and jetties.

• Avoid standing close to the edge or below cliffs, as coastal cliffs are susceptible to erosion and large portions of earth or rocks could crumble.

Let me know in the comments if you have any questions regarding either king tides or big waves on the Oregon Coast! I absolutely love this topic and am happy to discuss.