CatchWindow fishing intelligence

Nantucket Island, MA Daily Water Report — August 27, 2026

Thursday shapes up as a split decision around Nantucket: a top-tier morning for divers and sailors gives way to an afternoon that will test the patience of anyone in a small boat or kayak. The window is clear, but it’s narrow. The early hours are the play. Winds start light, barely a ripple, and the southeast swell is long and clean at 0.42 meters on a 7.65-second period. That combination pushes the diving score to 8.5, the best of anything today, and the sailing score to 8.2, a marked improvement over yesterday’s 6.6. If you’re underwater, that 21.3-degree water is running a third of a degree warmer than the recent average, and while the chlorophyll reading is elevated, the real draw is the calm surface and solid visibility. For sailors, the wind builds steadily through the morning, offering a consistent building breeze before it gets too punchy. By midday the south wind is gusting over 20 knots, and the wave heights climb from the calmest 0.58 meters at 2 a.m. to a representative 0.84 meters by afternoon. That shift robs kayakers—the score falls to 4.6, the lowest of the bunch—and knocks boating down to 6.1, well off yesterday’s 7.1. The surf score of 7.5 is respectable, but the wave period is short at 5 seconds, so it’s choppy, wind-driven stuff rather than clean groundswell. Fishing sits at 6.5, held back by the building wind and falling pressure, though the solunar minor period around 5:27 a.m. might reward an early line. The afternoon high tide timing is unclear without tide data, but the falling barometer and increasing south wind suggest the chop will only get messier as the day wears on. Dawn slips in at 5:33, and by sunset at 7:25, the wind should be easing. Looking ahead, Friday offers lighter peak winds and slightly smaller seas, with the diving and fishing scores likely to climb back toward recent highs. Saturday through Monday sees a building wind trend, with Monday’s forecast peak of 27 knots and a 31% chance of rain signaling a firm shutdown for small craft. Best bet: Get on the water at first light, because by lunchtime the south wind will have turned Nantucket Sound into your afternoon adversary.