Cyclone Tino's path across the Pacific is expected to send big swells and rips New Zealand's way from today - and there are fears weak swimmers could be caught unawares.
The cyclone was expected to be downgraded to an ex-tropical cyclone some time today, according to Weatherwatch.
While it would pass well to the east of New Zealand, it would be a bigger storm with lower air pressure, the forecaster said.
"This new deepening cold-centred low is what will be helping to create bigger waves and rips around eastern NZ in the days ahead."
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Dangerous beach conditions may be churned up on the east coast from Northland through to Wairarapa.
"While increased swells may not be that great compared to the more rugged West Coast storms, even an additional metre or so of wave height could create much more difficulty swimming with younger and older people and weaker swimmers etc, especially in beaches which may traditionally been seen as 'safe' and 'calm'."
MetService also anticipated swells of between 2-3m over Monday and Tuesday due to the large storm in the east.
Today's weather is expected to be settled across the country, with baking hot temperatures in much of the North Island.
Auckland and Hamilton had their hottest days of the summer on Sunday, but are tipped to get even hotter today, with 30C predicted in the Waikato and 28C in Auckland.
That hot, calm weather is expected to send people to the beach, prompting warnings from Surf Life Saving NZ.
Children, small dogs and the elderly were most at risk of being knocked over by huge waves today, the organisation warned. Surges could come up well past the high tide mark.
East Cape, Gisborne and Hawke's Bay would likely be most affected by the swells - but they would also be a little cooler with cloud and some drizzle, clearing in the afternoon or evening, according to Weatherwatch.
The South Island could also expect a sunny day although temperatures won't reach the extremes of the North Island.
Fine. Light winds. High 27C, Low 16C
Fine and warm. Light winds and afternoon sea breezes. High 28C, Low 17C
Fine and warm. Light winds and afternoon southwesterly breezes. High 30C, Low 13C
Fine. Light winds and afternoon sea breezes. High 27C, Low 17C
Fine. Light winds, but southwesterly breezes in the afternoon. High 24C, Low 13C
Cloudy with possible drizzle, but afternoon fine spells. Southerly breezes dying out. High 23C, Low 15C
Fine. Southerly breezes. High 26C, Low 13C
Areas of low cloud and fog, clearing to fine late morning. Southerly breezes. High 22C, Low 13C
Fine. Light winds and afternoon sea breezes. High 23C, Low 16C
Morning cloud and chance drizzle, then fine. Cloud returning in the evening. Light winds, but afternoon northeasterly breezes. High 22C, Low 14C
Some morning cloud, then fine. Cloud returning in the evening. Light winds and afternoon sea breezes. High 20C, Low 14C