Wellington Marine ForecastCook Strait
Updated Fri Sep 11, 2026
NO-GO weekend: steep chop, crossing seas, and building swell all three days
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Marine Forecast for Cook Strait Sep 11–13, 2026
📋 NO-GO weekend: steep chop, crossing seas, and building swell all three days
NO-GO Friday: NNW winds gust to 36 knots from 8:00 AM-4:00 PM, creating a confused cross-sea where SSW swell meets WNW wind-waves. Early morning and evening hours are calmer, but the midday window is dangerous for recreational vessels.
NO-GO Saturday: despite light 5-9 knots winds, SSW swell builds all day to a dangerous 11.6 feet at 11-second periods by evening. Large swell alone makes this unsafe regardless of the calm breeze.
NO-GO Sunday: leftover SSW swell remains 6.7-9.4 feet at 10-11 second periods all day despite light, pleasant 6-14 knots winds. Wave height alone keeps this day unsafe for recreational vessels.
This is a NO-GO weekend across the board. Friday brings a midday wind squall creating steep wind-wave chop, Saturday sees rapidly building 11-12 second SSW swell that overwhelms the coastline, and Sunday's swell remains at dangerous heights even as winds ease. None of these days offer a safe full-day window for recreational vessels.
Recent days at Cook Strait
Today’s Water at Cook Strait
Sea surface temperature and chlorophyll around Cook Strait, imaged fresh every morning. Water at the star is 56.2°F today, and chlorophyll of 0.33 mg/m³ reads as green shelf water at the spot.
Imagery: Sep 10, 2026 · rebuilt every morning
These charts show you the breaks. DeepCast reads them. A zone-by-zone AI fishing report for these exact waters — temperature edges, color changes, and structure, analyzed together — for $4.99.
Get the AI fishing reportSST and chlorophyll from the SeaLegs AI DeepCast satellite pipeline. Charts are a planning aid — always check the official marine forecast before making the run.
About Cook Strait
Wellington's boating is decided outside the heads, not inside them. The harbour is sheltered; Cook Strait is not, and it has a reputation for wind that it comfortably earns. This forecast covers the exposed water south of the entrance — the conditions you actually meet once you're clear.
It updates every morning from the latest marine model data, and each day gets an honest GO, CAUTION, or NO-GO call — the same AI rating used in the SeaLegs AI app.
Reading Cook Strait
The strait sits in the gap between the North and South Islands, and that gap does something specific to weather: it funnels and accelerates it. Wind moving through the strait is routinely stronger than the same system either side of it, which is why a forecast that looks unremarkable regionally can still be a hard day on the water here. Treat the strait's own numbers as the ones that matter.
Two things compound it. Tidal streams run strongly through the strait, and wind against tide is what turns a manageable sea into a steep and punishing one — so read wind direction against the tide, not wind speed alone. And a southerly has the whole Southern Ocean behind it, arriving as long-period swell with nothing in the way. Plan the return leg as carefully as the run out; the strait is not a place to be caught deciding late.
Cook Strait forecast FAQ
How is the sea at Cook Strait today?
As of Sep 11, 2026, the SeaLegs AI verdict for Cook Strait is NO-GO. Friday is a NO-GO day driven by a midday wind event: NNW winds ramp up from 20 knots to a peak of 27 knots with gusts to 36 knots between 8:00 AM and 4:00 PM, whipping up steep wind-wave chop that crosses the existing SW swell. Early morning (12:00 AM-7:00 AM) is calmer with winds easing to near-calm by 5:00 AM and waves 5-7 feet at 6-7 second periods from the south, but this is a narrow window bookending a dangerous midday period. The rationale specifically flags a confused cross-sea with SSW swell crossing WNW wind-wave during the peak wind hours, meaning two wave trains from different directions create awkward, uncomfortable, unpredictable motion with no comfortable heading - conditions ease again after 5:00 PM as wind drops to 8-14 knots.
Why is Cook Strait so windy?
The strait is a narrow gap between New Zealand's two main islands, and it funnels weather through it — wind accelerates as it squeezes through, so conditions in the strait are commonly stronger than the surrounding region's forecast suggests. That's the main reason a Wellington day has to be judged on the strait's own numbers.
Does this forecast cover Wellington Harbour?
No — deliberately. This forecast is aimed at the open water of Cook Strait south of the harbour entrance, because that's what decides whether a trip is on. The harbour itself is considerably more sheltered, and a forecast placed inside it wouldn't tell you about the water you're heading into.
How often is this forecast updated?
The page is rebuilt every morning from the latest model run, and the SpotCast card refreshes live in your browser. The date stamp above the outlook shows when it was last generated.
What do GO, CAUTION, and NO-GO mean?
GO means conditions are favourable for most recreational boats. CAUTION means marginal — manageable for experienced crews in capable vessels, but check the wind, tide and sea timing closely. NO-GO means conditions are hazardous for small craft and the trip is best postponed.
What is the water temperature at Cook Strait today?
As of Sep 10, 2026, the satellite-derived sea surface temperature at Cook Strait is about 56.2°F, with chlorophyll around 0.33 mg/m³ (green shelf water). The SST and chlorophyll charts on this page are rebuilt every morning from the SeaLegs AI DeepCast satellite pipeline.
More offshore forecasts
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