How to Read a Surf Forecast: Wave Height, Period, Wind and Tide Explained
A surf forecast packs a lot into a few numbers. Most people glance at the wave height and stop there, then wonder why a "4 ft" day was a mess. This guide explains each part of a typical forecast, how they interact, and how to turn them into simple rules for your own beach.
Wave height
Forecasts usually show significant wave height: roughly the average of the biggest third of waves. Individual sets can be noticeably bigger. Different sites measure in metres or feet, and surfers' own descriptions of size vary by region, so compare forecasts with what you actually see at your beach and build your own sense of what a number means there.
Swell period
Period is the time in seconds between waves passing a point. It tells you how much energy the swell carries:
- Under about 8 seconds: short-period wind swell. Often weak and messy.
- About 10-12 seconds: good groundswell for most beaches.
- 13 seconds and up: powerful swell that can wrap into sheltered spots and break much bigger than the height suggests.
A 1 m swell at 14 seconds can surf bigger than a 1.5 m swell at 7 seconds.
Wind speed and direction
Wind shapes the wave face. Offshore wind (blowing from land to sea) grooms waves clean; onshore wind (from sea to land) crumbles them. Light wind of any direction is usually fine. Direction depends entirely on which way your beach faces, which is why one forecast can be perfect at one spot and blown out at the next. More in offshore wind explained.
Tide
Many breaks only work at certain stages of the tide. A reef might need mid to high; a beach break might close out at high and work on the push from low. Note which phases work: low, mid rising, mid falling or high. Tides also shift by roughly an hour a day, so the good tide moves through your week.
Putting it together
A good day is when all of these line up inside the time you can surf. Write simple rules per beach, for example: 2-5 ft, wind under 20 km/h from N, NE or E, mid rising or high tide. Then check forecasts against those rules a few days ahead.
If you'd rather not do that every day, SurfSlot's surf calendar lets you save these exact rules per beach and watches the forecast for you. When a window matches your free time, it emails or texts you, or blocks the session in Google Calendar.
Frequently asked questions
What is a good swell period for surfing?
For most beaches, around 10 seconds or more is a good sign. Shorter periods tend to produce weaker, messier waves.
How far ahead are surf forecasts reliable?
Broadly, the next two to three days are the most reliable, with forecasts becoming less certain further out.