May's rain 'phenomenal', says NIWA

"Phenomenal" rainfall and flooding in the north of New Zealand contrasted with more sun in the South Island during May, according to the National Institute of Water and Atmospheric Research's climate summary for the month.

Tauranga experienced its wettest month for any time of the year for more than a century, with 634mm of rain falling, Niwa climate scientist Jim Salinger said.

More than half of this total, 347mm, fell on May 17-18, causing widespread flooding in Tauranga and devastation in the Bay of Plenty township of Matata.

Dr Salinger described the flood-producing rain as "phenomenal" and "unprecedented", breaking records which began in 1910.

The cost of the flooding damage has been estimated at $40-$50 million.

Conditions were also very wet on the Coromandel Peninsula and in Hawke's Bay, with above average rainfall recorded in Auckland, Waikato, Taranaki, Gisborne, Wellington, Marlborough, and parts of Northland and north Canterbury.

Dr Salinger said the Big Wet was caused by depressions often centred northwest of the North Island, with anticyclones occurring well away to the east or west of the country. This led to more frequent northeasterlies bringing the wet conditions.

However, the news was not bad for everyone. Sunshine hours were well above average in inland south Canterbury and coastal areas of both Southland and Otago.

Of the four main centres, Dunedin was the driest and Auckland the warmest.

May was much warmer than usual across the country, with mean temperatures 1-1.5degC above average in the North Island, and .5deg C warmer in the South Island.

Fog hit Wellington airport again on May 19 and 20, bringing the total for the year to 48 hours -- the highest in 45 years of recording.

- NZPA