How days are picked
The rules
Take every predicted low for the beach's NOAA station for the year.
Keep a low only if it falls at least 30 minutes after sunrise and at least 30 minutes before sunset at the beach.
Grade it by its height against the chart's zero, mean lower low water: low at 0.0 ft or lower, very low at -1.0 ft or lower. Where a park or agency names its own height for a beach, that beach uses it and names the source.
Keep one day per date: the lowest low that passes.
Give a window from about one hour before the low to one hour after, cut to daylight. For stations NOAA works out from a reference station, times are estimates and the page says about.
Name the station on every beach page, with its distance from the beach and whether it sits on the open coast, in a harbor, in a bay or at a river mouth.
Sunrise and sunset are worked out for each beach's own coordinates with NOAA's solar formula.
What the site never claims
- That the water reaches the predicted level. Wind, swell and air pressure move the real level, so every height here is a prediction.
- Anything about what lives in the pools, whether you may enter or collect, or how to keep yourself out of harm. Each beach page links the agency that manages it.
- That a razor clam dig is open. In Washington, digs happen only on dates the state approves after toxin tests.
- That NOAA endorses this site.