The best way to check the surf in Hawaii is to wake up very early in the morning and look at it in person. If you can’t look at the ocean physically, the next best option is to go online and visit either Surfline or Surf News Network to look at their surf cams and forcast. I like the Surfline surf cams better, but the surf forecast and report from Surf News Network is more accurate. So your best bet is to check them both.
When you check online, you also get information on tides and winds. For the North Shore, you want to avoid winds over 25 knots and those with a westerly direction. Tides are usually not that important unless the waves are super small, 1 foot or less, or if they are super big, over 15 ft., in both cases, you want to avoid the King tides.