Northlanders praying for decent rain will get just that from today as a low brings downpours and humidity to most parts of the region.

MetService meteorologist Rob Kerr said a severe weather watch was in place for Northland and northeast parts of Auckland, including Great Barrier Island, from 6am to midnight today, with a possibility rainfall levels may reach warning criteria.

About 80mm of rain needs to fall before that criteria is reached.

"There's a concern that some of Northland could have that much rain, particularly in the north and east. Temperatures would be quite warm until Sunday night and into Monday, when it will be noticeably cooler," Kerr said.

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He said Cyclone Oma was likely to stay in the Coral Sea off the Queensland coast but either way, New Zealand would be on the receiving end of some heavy rain and strong winds.

The cyclone is expected to move southwest away from New Caledonia in the next two days. It is then expected to move southwest towards the southern Queensland coast.

Heavy rain, winds and storm surges from the cyclone uprooted trees, destroyed homes and food crops in Torba and Sanma provinces in Vanuatu.

Kerr said daytime temperatures in Northland this weekend were likely to hover in the mid 20s, dropping down to around 20C on Sunday and into Monday while the mercury at night would be between 11C and 13C.

Weather could become more fierce on Sunday in central New Zealand as the low was expected to deepen, bringing rain and strong south to southwest winds.

On Monday, the low should move away to the east allowing a ridge of high pressure to slowly spread across the country from the west, with the wind and rain easing.

People are advised to keep up to date with forecasts in case parts of the watch are upgraded to a full warning, or further areas are added.