May's climate

New Zealand climate in May

Rainfall (click to enlarge).

Temperature (click to enlarge).

More frequent northwesterlies than usual were recorded over much of New Zealand in May. It was the warmest May in over 140 years of measurement, with a national average temperature of 1.7 °C above normal. Rainfall was well below normal in the north and east of the country, and well above normal in Nelson. The month was sunnier than usual in many North Island and eastern South Island locations.

For more information on the climate in May 2007, visit the climate summaries page at www.niwascience.co.nz/ncc/cs/mclimsum_07_05

Deficits remain

Soil moisture (click to enlarge).

Soil moisture deficits of more than 70 mm remained along the east coast of the country at the end of May. Deficits of more than 110 mm remained in Hawke’s Bay and inland Otago. This is in marked contrast to normal conditions at the end of autumn, and to the relatively wet conditions of a year ago.

 

Generally below normal stream flows

River flows (click to enlarge).

May stream flows were normal to above normal in Nelson, Marlborough, and the west of the South Island, and below normal elsewhere.

March to may: the climate we predicted and what happened

(click to enlarge).

Rainfall

Rainfall was mostly lower than predicted, apart from areas, of Northland, Waikato, and the north and east of the South Island, which recorded normal rainfall.


(click to enlarge).

Air temperature

Air temperatures were correctly predicted in the north and west of the North Island, and the north of the South Island. In most other places, autumn was warmer than expected.


(click to enlarge).

River flows

Streamflows were above normal in the far north, as was predicted, but mostly below normal elsewhere.


The three outcome maps give the tercile rankings of the rainfall totals, mean air temperatures, and mean river flows that eventuated from March to May, in comparison with the forecast conditions.

As an approximate guide, middle tercile rainfalls typically range from 80 to 115% of the historical normal, and middle tercile temperatures range about the average by plus or minus 0.5 °C.