Hawke's Bay is set to get the heaviest downpour since Easter and just in time to save the region from a potential winter drought.

A heavy rain warning is in place for Hawke's Bay, particularly south of Napier, which will remain in place until about midday today.

MetService meteorologist Michael Martens said the rain began picking up from midday yesterday, with most areas in Hawke's Bay experiencing between 10mm and 20mm.

Some areas in the ranges had more than 30mm.

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In the past couple of days, Mr Martens said 17mm had fallen at Napier airport - 13mm of this was recorded in eight hours yesterday.

That was similar to rainfall figures in other central areas of Hawke's Bay, he said.

Overnight and this morning, 80-100mm of rain was expected, especially about the eastern hills.

Hawke's Bay Civil Defence group manager Ian Macdonald said they had been monitoring river levels.

He said the river channels were low so there was room for the expected rain.

Mr Macdonald said had the rain been forecast to fall within a shorter time frame, there could have been issues.

"This is actually perfect. If anything, I was more worried about the possibility of a winter drought.

"We were actually in the initial phases of planning for drought."

He said south of Napier, where the most rain was expected, was the driest part of the region.

Most of the North Island will be waking up to a wet Thursday morning, with rain forecast in most places.

Some school sport was cancelled last night and some public transport services were delayed due to the rain.

Mr Martens said a maximum of 14C was forecast for yesterday but the mercury only reached 12C.

Napier is forecast for a high of 17C today, dipping down to an overnight low of 6C.

Hastings is forecast for a slightly cooler 16C but is forecast to have the same overnight temperature as Napier.

The rain is expected to ease this evening.