Even if the deadly Tropical Cyclone Winston does not head our way, Northland will feel its effects by Friday through strong easterlies, high swells and flooding mostly on the east coast.

After wreaking havoc on Saturday in Fiji where at least 20 people were killed, the category 5 storm was yesterday downgraded to category 4 as it headed south towards New Zealand.

Cyclone Winston was yesterday morning lying about 490km west of Nadi and was forecast to maintain category 4 status through today as it heads south.

MetService has warned the cyclone could affect central and northern parts of the North Island during the weekend but it would not have the same impact and level of destruction as it did in Fiji and earlier on in Tonga.

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Cyclone Winston made landfall in Fiji on Saturday as a category 5 storm, bringing wind gusts of up to 325km/h and average winds of 230km/h.

"But with all tropical cyclones, there remains some uncertainty associated with the forecast track," meteorologist Georgina Griffiths said.

There was a "fairly solid" chance the cyclone would come near northern New Zealand by this weekend.

"At category 3, it's still a significant system and on a southerly track it could come closer to the North Cape or somewhere in the middle of the Tasman Sea if it heads more towards Australia," she added.

"Either way, Northland will be the first to feel its effects. The easterly winds will pick up but there won't be gales. Easterly swells will increase with possible storm surge and onshore winds."

Ms Griffiths said the already-stifling humidity experienced throughout the country but particularly in Northland would get worse as the week progressed.

She said with the tropics so abnormally warm from the effects of El Nino, tropical cyclones were inevitable.

"Winston did a really big loop in very warm Pacific waters and because of the prevailing warm weather, it can get its energy from anywhere but we're not likely to see its effects before Friday."

Weather watches or warnings can be accessed at metservice.com, on m.metservice.com, MetService TV, at MetService New Zealand Facebook, @metservice and @MetServiceWARN on Twitter and at blog.metservice.com.

Meanwhile, a Whangarei truck driver who was stranded in Suva was expected to fly out of Nausori Airport yesterday. According to a family member, Rabendra Prasad was rescheduled to board a Fiji Airways flight at 9am yesterday.