Northland could be heading for its warmest May on record, with daily highs falling below 20C on only one day so far this month.

But the MetService warns the Indian summer Northland is experiencing won't last, with temperatures set to drop from the end of next week. Until then, Northland can expect temperatures that are much higher than normal for the time of year, Metservice Meteorologist Tom Adams said.

However, a deep low moving onto the North Island from the west Saturday evening could bring a belt of severe west to southwest gales over Northland.

Since the start of May, Northland has recorded two days where the maximum temperatures were 24C and six more over 23C. The historic May mean daily temperature is 14.7C and, if the weather from the first half to the month continues, that will be exceeded this year.

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The May record high temperature of 24.3C in 2004 and 2007. With the official temperature recorded in a louvred box at Whangarei Airport, the temperature inland will likely be several degrees higher.

Mr Adams said that official high is unlikely to be reached this month, but daily highs of 20 or above for the first half of the month was unusual.

As well, he said, the daily low temperatures for the region had not fallen below 12C overnight so far this month, making for a far warmer than normal night time for the month.

"Next week is looking like the temperatures will drop a bit up there. Not by as much as some places further south, where there will be quite a drop, but you'll still notice it being colder," he said.

"But it's likely that even though it will be colder than now, those temperatures will still be a bit above normal for the time of the year."

Mr Adams said temperatures across the country had been higher than normal throughout April and into May, thanks to tropical weather coming from the north.

In April, Whangarei had a mean daily temperature of 17C - above the normal of 16C.