Surfers on the West Coast are in for a thrill this weekend with 8m waves on the horizon.
Unsettled southwesterlies will increase in intensity overnight, which are expected to rise from 25 to 35 knots by Friday morning.
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The gusts will whip up the water with swells of up to 8m predicted, creating what MetService calls a "very rough" sea off the coast of Greymouth.
There's also the possibility of squalls, thunderstorms and hail, making for poor visibility.
Further down the coast at Milford the wind will be even stronger, peaking at 45 knots by late Friday morning.
On Wednesday NIWA predicted swells of more than 10m, however, they look like they'll be slightly smaller but still very impressive.
NIWA says the large waves combined with king tides (expected between Thursday and Tuesday) mean an increased risk of coastal erosion and flooding.
There's a storm warning in place for Puysegur down the bottom of the coast. Friday morning will see the region lashed by 50-knot winds and the possibility of hail. The dramatic weather should ease by Sunday.