The Wave Height Forecast service is provided by SurferToday.com and powered by NOAA.
Check the wave height surf report for the next seven days. Select your surf forecast region:

 

 

The technical notice made by NOAA:

The significant wave height is a measure for the wave height, and closely corresponds to what a trained observer would consider to be the mean wave height. Note that the highest wave height of an individual wave will be significantly larger.

NOAA - National Oceanic and Atmospheric Administration