Conditions are ideal for a tropical cyclone to form north of New Zealand and potentially create dangerous swimming conditions on our beaches.

Fiji was currently lying bang in the storm's predicted firing line, with Tonga also potentially in its path, international forecasters said.

It was then tipped to track close to New Zealand's east coast by next Monday.

Luckily, a high pressure system plonked over the country would likely protect us from any severe weather, forecaster WeatherWatch said.

Yet the deceptively calm conditions could still hide dangers on our beaches.

It meant that while the weather overhead might be "hot, sunny and calm with no indication of a storm", the cyclone could still bring deadly underwater forces, WeatherWatch said.

"There are a number of incidents in recent years, some led to drownings others led to near-drownings when offshore storms like this churn up stronger rips and bigger waves at our most populated eastern beaches," the forecaster said.

"These dangerous beach conditions can catch people off guard, especially if they are unaware of increased energy in the water due to the offshore storm."

The storm could also influence New Zealand's prevailing winds after the country has been buffeted by weeks of westerlies.

"By next Monday a very deep and sizeable storm (extra-tropical) should lie east of the North Island, close enough to bring an enhanced southeast winds flow and bigger swells from the east," WeatherWatch said.

"This may be good for some surfing spots - but remember this storm will bring more dangerous beach conditions to the east from Northland to Coromandel, Bay of Plenty to East Cape, Gisborne and down to Hawke's Bay and maybe even Wairarapa."

The cyclone would likely be much more damaging in the tropics with heavy rain, slips, flooding and damaging, strong winds possible in Fiji.

Tonga could be hit with a surge of heavy rain, strong to gale-force winds and rough seas.