A minus tide is any low tide predicted to fall below 0.0 ft MLLW — "Mean Lower Low Water," the long-run average of each day's lowest tide. It exposes reef, sandbar, and tidepool zones that stay submerged the rest of the month. Minus tides aren't rare in bulk: NOAA predictions give the 11 West Coast stations Tidewindow tracks 940 of them in 2026. What's scarce is one you can see — 535 of those (57%) overlap daylight.
What does 0.0 ft actually mean?
US tide predictions measure height against a datum called MLLW. NOAA takes each day's lower low tide (many US coasts, including the entire West Coast, get two lows of unequal depth per day) and averages it over a 19-year period called the National Tidal Datum Epoch — currently 1983 through 2001. That average becomes 0.0 ft, and it's the reference for US tide predictions and nautical chart depths.
So a "0.0 ft" low isn't unusually low — it's average. The interesting days are the ones below it:
| Predicted low | What it means |
|---|---|
| +2.0 ft | An ordinary, unremarkable low tide |
| 0.0 ft | About average for a daily lowest tide |
| −1.0 ft | A genuine minus tide — big intertidal exposure |
| −2.0 ft and below | The handful of best days of the year |
Illustrative bands relative to the MLLW datum, not station predictions. Every actual height on this site comes from NOAA's published harmonic predictions.
Why do minus tides come in clusters?
Tides are driven by the combined pull of the moon and sun. Around new and full moons, the two line up and their effects stack — these are spring tides (a historical term for the tide "springing forth," nothing to do with the season), when highs run a little higher and lows run a little lower. Around quarter moons the pulls partly cancel (neap tides) and everything flattens out.
The practical result: minus tides arrive in runs of a few consecutive days, roughly twice a month, centered on the new and full moon. And some months' runs are much deeper than others, because the moon's distance from Earth stacks on top. When a new or full moon coincides with perigee — the moon's closest approach — you get a perigean spring tide, which NOAA says happens six to eight times a year. Those are the months the tide table goes memorably negative.
How many minus tides actually happen in daylight?
A minus tide at 3 AM helps no one with a tide pool plan. So the honest way to count minus tides is to count the visible ones — and here 2026 offers a clean comparison between the two coasts Tidewindow computes:
| Coast | Stations tracked | Minus tides, 2026 | In daylight | Daylight share |
|---|---|---|---|---|
| West (WA, OR, CA) | 11 | 940 | 535 | 57% |
| East (Bar Harbor, ME) | 1 | 90 | 52 | 58% |
Computed 2026-07-03 from NOAA predictions at the 12 stations Tidewindow tracks; east coast figures are NOAA station 8413320 (Bar Harbor, ME).
Two things stand out. First, the volume: 940 minus tides across 11 West Coast stations works out to about 85 per station for the year, and Bar Harbor alone logs 90 — more than the Pacific per-station average. Second, the daylight share barely differs between coasts: 57% west, 58% east. Roughly four in seven minus tides are visible ones, whichever ocean you face. Add the coasts together and 2026 holds 587 daylight minus tides across the 12 stations; the other 443 happen in the dark.
Where the coasts genuinely diverge is not whether the good lows land in daylight but when in the day they do. You can watch these shares shift month by month on the daylight-minus-tide index.
When in the day do daylight minus tides land?
On the West Coast, mornings dominate. The three busiest hours for a daylight minus low in 2026 are 6 AM (56 events), 7 AM (52), and 5 PM (51), and about half of all 535 daylight minus lows — 269 of them — fall between 3 and 9 AM. The distribution is a two-humped day:
| Time of day (West Coast) | Daylight minus lows, 2026 | Share |
|---|---|---|
| Morning (3–9 AM) | 269 | 50% |
| Midday (10 AM–2 PM) | 75 | 14% |
| Afternoon (3–8 PM) | 191 | 36% |
Computed 2026-07-03 from NOAA predictions at Tidewindow's 11 West Coast stations.
The midday trough is real: set aside the sparse edge hours right at dawn and dusk, and 11 AM and noon are the two quietest hours of the core daytime, with 11 minus lows apiece all year — a fifth of what 6 AM delivers. That is the arithmetic behind the West Coast tidepooler's reputation as a dawn person. To see where your station's humps sit across the calendar, the year heatmap draws all twelve months at once.
Bar Harbor runs the other way. Of its 52 daylight minus lows in 2026, 34 — about 65% — land between 1 and 7 PM, with 4 PM the single busiest hour (9 events). Same daylight share as the Pacific stations, opposite end of the day. If your habit is coffee first, Maine agrees with you.
The lesson for reading any raw tide table: don't scan for negative numbers; scan for negative numbers you can actually see. That intersection — low enough and light enough — is exactly what this site computes, scored 0–100 for every window, straight from NOAA's harmonic predictions and the sun's computed position.
What to do with one
The Tide Window Finder gives every upcoming window an arrive-by time, set an hour before the predicted low: arrive then and you follow the water out, get the deepest zone at slack, and walk back in with the flood. The methodology page shows every formula involved — that arrive-by rule included — and exactly where "daylight" begins and ends in the counts above.