A tide table gives you two facts per line: a time and a height measured from a zero called MLLW. Everything you plan around — how long the beach is walkable, whether it's light out — must be computed. At NOAA station 9435380 (Newport, OR), the entry for August 12, 2026 read −1.9 ft at 6:46 AM. Computed out, that one line became a 285-minute window, 4:30 to 9:15 AM, with 179 daylight minutes.
What does the height number actually mean?
The feet on a tide table are not water depth. They are the predicted height of the sea surface relative to a fixed local zero called a datum. US tide predictions use MLLW — Mean Lower Low Water. NOAA takes each day's lower low tide and averages it over a 19-year span called the National Tidal Datum Epoch, currently 1983 through 2001. That average becomes 0.0 ft.
This sets the intuition everything else hangs on: 0.0 ft is not "no water." It is an ordinary day's lowest water. A +6 ft high tide means the surface sits six feet above that mark. A −1.9 ft low means the surface drops nearly two feet below the average daily minimum, and ground that stays submerged through most low tides gets a few hours of open air. The negative numbers are the ones worth circling — with one catch this article keeps returning to. In Tidewindow's July–December 2026 data for Newport, the deepest low with a real daylight window, −2.522 ft, came and went on July 15, and August 12's −1.913 ft followed it. The deepest lows still ahead on the 2026 table — December 24 at −2.118 ft and November 25 at −2.077 ft — both bottom out about two hours after sunset, with under 20 daylight minutes at the very front of their windows. The deepest remaining low whose window clears 30 daylight minutes is December 23's −1.91 ft, and it appears again below.
Why does the table list two lows a day, and why is one deeper?
Because on the US West Coast the tide is mixed semidiurnal: two highs and two lows of different size every lunar day, in NOAA's classification. A Newport tide table typically shows four events per date, and the day's two lows can sit far apart in height. The datum already told you which one matters — it is Mean Lower Low Water — and so should your plan. The lower low opens ground; the higher low is often barely an event. Every low quoted in this article is a day's lower low.
The good lows also arrive in runs. Around new and full moons, the sun's pull stacks with the moon's — spring tides, when, as NOAA puts it, "high tides are a little higher and low tides are a little lower than average" — so lows deepen for several consecutive days, then flatten toward the quarter moons. One such run is in the next table.
How do you read one real row?
Take Wednesday, August 12, 2026 — the deepest daylight low of Newport's August run. The dates have passed, but the row stays here as a worked example because it teaches every part of the exercise. The raw table row said, in effect, Low — 6:46 AM — −1.9 ft. Standing on the sand at South Beach, here is what each part meant:
- −1.913 ft. At the bottom of the tide, the surface sits nearly two feet below the long-run average of daily lowest tides. Ledges and boulder fields that a 0.0 ft low never uncovers are briefly walkable.
- 6:46 AM. The single minute of minimum water — not the visit. The tide is low enough for a long stretch on either side of it.
- What the row doesn't say. Computed against the walkable threshold and the sun, this low opened a window from 4:30 AM to 9:15 AM: 285 minutes, 179 of them after sunrise. Arriving by 5:46 AM, an hour ahead of the low, meant following the water out and walking back in with the flood.
Now the run that row sits inside:
| Date | Lower low (ft MLLW) | Time of low | Walkable window | Daylight min | Score |
|---|---|---|---|---|---|
| Mon, Aug 10 | −1.374 | 5:10 AM | 2:55–7:40 AM | 87 | 62 |
| Tue, Aug 11 | −1.761 | 6:00 AM | 3:45–8:30 AM | 136 | 78 |
| Wed, Aug 12 | −1.913 | 6:46 AM | 4:30–9:15 AM | 179 | 88 |
| Thu, Aug 13 | −1.788 | 7:28 AM | 5:20–9:50 AM | 213 | 86 |
| Fri, Aug 14 | −1.378 | 8:06 AM | 6:05–10:15 AM | 237 | 83 |
| Sat, Aug 15 | −0.714 | 8:43 AM | 7:00–10:30 AM | 210 | 74 |
Computed from NOAA station 9435380 (South Beach, Newport, OR) predictions; every row re-verified 2026-09-25 against Tidewindow's current data, unchanged.
Two patterns here hold at every station, so they are worth internalizing. First, the lows deepen toward the middle of the run and relax after — the shoulder days, August 11 and 13, differ by under three hundredths of a foot. Second, each day's low lands later than the last, by 37 to 50 minutes across this run; the tide keeps its own clock and drifts against ours. If Wednesday at 6:46 didn't fit your week, Thursday at 7:28 nearly repeated it. August was a generous month for this: Newport's August calendar listed 32 lows below +1.0 ft, and 17 of the walkable windows around them held at least 30 daylight minutes, 13 of those at minus tides.
Why isn't the lowest number automatically the best day?
Because a tide table is silent about the sun. The deepest row of the run above has a near-twin on the December page of the same tide table, and the pair makes the point better than any argument:
| Wed, Aug 12 | Wed, Dec 23 | |
|---|---|---|
| Predicted lower low | −1.913 ft | −1.910 ft |
| Time of low | 6:46 AM | 5:53 PM |
| Walkable window | 4:30–9:15 AM | 3:40–8:20 PM |
| Daylight minutes in window | 179 | 60 |
| Window Score | 88 | 61 |
Computed from NOAA station 9435380 (South Beach, Newport, OR) predictions; both columns re-verified 2026-09-25 against Tidewindow's current data, unchanged.
On the tide table these are twins; the depths differ by 0.003 ft. On the beach they are not. The August low bottomed out mid-morning and handed you three hours of lit, walkable shore. The December window runs 280 minutes but only 60 of them in daylight — all at the front end, while the water is still on its way down. By the 5:53 PM low itself, the light is gone. And yet that December 23 row is now the deepest low left on Newport's 2026 table with a meaningful daylight window: the two deeper lows still ahead, December 24 and November 25, bottom out well after dark. Scanning a printed table for the year's most negative number would send you to the beach in the dark.
That is the hidden filter in every tide table: depth and daylight are separate columns, and the table only prints one of them. To read it properly you'd check sunrise and sunset against every candidate row, every time.
Is the Window Score just a shortcut?
Yes. That is the design, and it is worth being plain about. The score compresses the arithmetic above into a 0–100 rating: how deep the low goes, how much of the walkable window overlaps daylight, and how the timing sits within the day. August 12's 88 ("Great") and December 23's 61 ("Good") are the two tables above, pre-computed. Every input is either a NOAA harmonic prediction or the sun's calculated position, and the formulas are public on the methodology page.
Be equally plain about what the score is not. It knows nothing of swell, wind, rain, fog, or how carefully you move on wet rock. A 90 during a storm is still a bad trip. The score ranks tide-and-light geometry, nothing more — it saves you the sunrise arithmetic, not the judgment.
Used that way, it turns table-reading from a chore into a glance. The Tide Window Finder lists upcoming windows with their arrive-by times, the Trip Picker compares candidate days side by side, and the Newport station page keeps the running calendar for spots like Yaquina Head and Otter Rock.
None of this replaces the tide table; it finishes it. Read the height against MLLW, trust the lower low, then do the daylight arithmetic — or let a score that shows its work do it for you.