Coming months to be warmer - with potential downpours

Days after record rainfall hammered the West Coast, climate scientists have warned of the potential for more big downpours over the next three months.

Niwa was also picking above-average temperatures that have persisted past summer to hang around over much of the country, and right into the first month of winter.

Niwa's climate outlook for the next three months forecast air temperatures to be above average in the north and east of the North Island and east of the South Island.

Everywhere else, temperatures were equally likely to be above or near average.

The balmy forecast didn't mean there wouldn't be cold snaps and frosts – especially in cooler places – during the slide into winter.

Rainfall levels were meanwhile likely to be above or near normal in the west and north of the South Island - and about equally likely to be below or near normal elsewhere.

Niwa further reported that well-above average coastal and Tasman Sea surface temperatures - including marine heatwave conditions – were forecast to have a strong influence on regional temperatures, and these could also drive big rainfall events.

That came after most weather stations along the West Coast recorded just under 200mm during a heavy downpour between late Sunday and early Monday.

Cropp Waterfall station recorded an incredible 1086mm of rain in 48 hours - the highest level for that time period on record, and nearly the entire average annual rainfall for Auckland, which was about 1200mm.

Niwa expected the April to June period to kick off with mixed air flows, higher pressure than normal in the northern Tasman Sea, and lower pressure than normal south of New Zealand.

This was predicted to result in more westerly quarter winds than normal, particularly during the second half of the coming season.

However, the risk to New Zealand of tropical cyclones remained normal – an average one of these systems was expected this season, but none had arrived so far.

Elsewhere in its report, Niwa said soil moisture levels and river flows were most likely to be below normal in the north of the North Island and east of the South Island.

Source / NIWA

But in the west of the South Island, soil moisture levels and river flows were most likely to be above normal.

In the north of the South Island, soil moisture levels and river flows are most likely to be in the near normal range, and for the west and east of the North Island, soil moisture levels and river flows were about equally likely to be below or near normal.

Source / NIWA

In the background, a central Pacific El Niño event continued during March as the ocean and atmosphere remained "weakly coupled", Niwa said.

"Sea surface temperatures warmed across the equatorial Pacific during March and El Niño is expected to continue during the upcoming three-month period."