East Coast tides are semidiurnal — two nearly equal lows a day — on a range more than double Southern California's: an 11.37 ft great diurnal range at Bar Harbor (NOAA station 8413320) versus 5.33 ft at La Jolla (station 9410230). The result: Bar Harbor gets 7–10 daylight minus tides every month from July through December 2026, no summer-only season required, and the same −1.0 ft reading buys about twice the relative exposure in SoCal that it does in Maine.
If you learned tide pooling on the Pacific coast, the East Coast will quietly break most of your habits. The lows come at different hours, the "good" months are different, and the tide table's negative numbers mean something else. Here's the math, worked from NOAA predictions for one station on each coast.
What makes East Coast tides different?
NOAA sorts tide patterns into three types, and the coasts split cleanly: "a semidiurnal pattern is more typical of the East Coast," while "the U.S. West Coast tends to have mixed semidiurnal tides." Semidiurnal means two highs and two lows a day of roughly equal size. Mixed semidiurnal also means two of each, but they differ in height — one low is the lower low, and it does most of the tide-pooling work.
Both patterns march to the same drummer: the lunar day is 24 hours and 50 minutes, so tides arrive roughly 50 minutes later each day. You could watch that drift in Bar Harbor's mid-July run — the morning minus low landed at 5:01, 5:56, 6:49, 7:41, then 8:31 AM across July 14–18, sliding 50 to 55 minutes per day (NOAA station 8413320 predictions, re-verified 2026-10-03).
The difference is what the drift does to daylight. On a semidiurnal coast, both daily lows are usable, so as they sweep around the clock every fortnight, some always cross daylight — in any season. On a mixed coast, only the lower low is deep enough to matter, and its clock position is locked to the season: mornings in summer, afternoons in winter, and stranded in darkness in the shoulder months.
How much bigger is the range in Maine?
More than double, per NOAA's published datums for the two stations:
| Datum | Bar Harbor 8413320 (ME) | La Jolla 9410230 (CA) |
|---|---|---|
| Mean range of tide (MN) | 10.56 ft | 3.69 ft |
| Great diurnal range (GT) | 11.37 ft | 5.33 ft |
NOAA published datums, 1983–2001 National Tidal Datum Epoch, re-verified 2026-10-03.
Physically, that means an ordinary Bar Harbor low sits at the bottom of a ten-and-a-half-foot drop twice a day. You don't need a minus tide to find exposed rock in Maine; the everyday intertidal apron is already enormous. At La Jolla the whole vertical show averages under four feet from mean high to mean low, so the extra inches below zero are where the interesting seafloor lives.
Why does a −1.0 ft rule read differently by coast?
Both stations measure against MLLW, the long-run average of each day's lowest tide (the methodology page covers the datum in detail, and the daylight-minus-tide index tracks the coast-wide counts). Because MLLW is a local average, the datum absorbs the range difference: the deepest lows with daylight windows in our July–December 2026 data are −1.65 ft at Bar Harbor and −1.88 ft at La Jolla — both, pleasingly, on December 24. One asterisk, though: La Jolla's low arrives at 3:47 PM with about an hour of daylight to spare, while Bar Harbor's arrives at 4:41 PM — its window's 68 daylight minutes run out around 3:58 PM, so the deepest moment itself lands in twilight.
What the datum can't absorb is the relative payoff. A −1.0 ft low deepens Bar Harbor's typical 11.37 ft full drop by about 9%. The same −1.0 ft at La Jolla deepens a 5.33 ft drop by about 19%. So a West Coast rule of thumb like "only bother below −1.0 ft" translates poorly to Maine, where a +0.5 ft low still uncovers more vertical rock than SoCal's best day of the year.
| July 2026 head-to-head | Bar Harbor 8413320 | La Jolla 9410230 |
|---|---|---|
| Tide pattern (NOAA) | Semidiurnal | Mixed semidiurnal |
| Lows below +1.0 ft | 35 | 26 |
| Daylight minus tides | 9 | 12 |
| Best window | Fri Jul 17, −1.1 ft at 7:41 AM (score 77) | Wed Jul 15, −1.5 ft at 4:54 AM (score 68) |
| Deepest low with a daylight window, Jul–Dec 2026 | −1.65 ft, Dec 24, 4:41 PM (after sunset) | −1.88 ft, Dec 24, 3:47 PM (in daylight) |
July 2026 is now history; recomputed 2026-10-03 from NOAA station 8413320 and 9410230 predictions, station-local dates.
Note the timing in that middle row: La Jolla's best July window was built around a 4:54 AM low, with only 113 of its minutes in daylight. Bar Harbor's best low arrived at a civilized 7:41 AM with 195 daylight minutes around it.
When should you tide pool on the East Coast?
The short answer for "when": almost any month, usually in the afternoon. The long answer is in the monthly counts of daylight minus tides:
| Month (2026) | Bar Harbor 8413320 | La Jolla 9410230 |
|---|---|---|
| July | 9 | 12 |
| August | 10 | 2 |
| September | 10 | 0 |
| October | 7 | 6 |
| November | 8 | 12 |
| December | 8 | 16 |
Daylight minus tides per month (windows with ≥30 minutes of daylight overlap), recomputed 2026-10-03 from NOAA station 8413320 and 9410230 predictions. July–September are complete; October–December are predictions.
La Jolla swings from 16 in December to zero in September — in that September, 29 lows dipped below +1.0 ft and not one minus low touched daylight. Bar Harbor never leaves the 7–10 band. Across July–December 2026, Bar Harbor gets 90 minus tides with 52 daylight windows (58%) — the same share as the 58% (548 of 953) across our 11 West Coast stations. The share matches; the calendar shape doesn't.
The clock shifts too. The busiest daylight minus-tide hour across our West Coast stations in that span is 6 AM (58 events); at Bar Harbor it's 4 PM (9 events), and 34 of the station's 52 daylight minus lows (65%) land between 1 PM and 8 PM. East Coast tide pooling is more often an after-lunch habit than a dawn patrol.
That July run this article was written around — back-to-back mornings on July 16 (−1.3 ft at 6:49 AM, score 76) and July 17 (−1.1 ft at 7:41 AM, score 77) — is now history, and the afternoon pattern has taken over on schedule. Next up on the Bar Harbor October calendar: consecutive afternoons on Friday October 9 (−0.4 ft at 4:37 PM, score 54) and Saturday October 10 (−0.5 ft at 5:23 PM, score 57), then Sunday October 25 (−0.6 ft at 4:43 PM, score 59), the best window of the next 60 days. The species lists differ as much as the tides: recent observations near Bar Harbor run to Common Periwinkles (20 reports), slippersnails and dogwhelks, while La Jolla's recent list is still wall-to-wall nudibranchs, led by 68 reports of Hamann's Aeolid.
One caution scales with the range: an 11 ft flood comes back fast. The National Park Service's tidepooling guidance for Acadia puts the usable window at "1.5 hours before to 1.5 hours after low tide" and advises that "it is best to start tidepooling before low tide and to leave as the tide is rising." They also note that "black rocks and seaweed are especially slippery." Treat the arrive-by times in the Tide Window Finder as the start of your exit plan, not just your entrance.