Current Climate - May 2013

May 2013 was characterised by lower pressures than usual over and to the east of New Zealand, with higher than normal pressures to the southwest of the country. This meant more northwesterly winds than normal affected the North Island, and more southeasterly winds than normal affected the South Island. It was a warmer than usual month for much of the North Island, due to this air flow. Very cold southerly air flow resulted in widespread snowfall over Southland, Otago, and parts of Canterbury, as well as the Central Plateau, as well as low temperatures and high winds to the North Island, on 27-29 May. 


Almost two-and-a-half times the normal May rainfall was recorded in Auckland – it was the wettest May on record for Auckland and Pukekohe. Almost double the normal rainfall for May was experienced in parts of Waikato. Rainfall was also well above normal (above 150 percent of May normal) in New Plymouth and parts of Marlborough, Canterbury, and Otago. Rainfall was above normal (120-150 percent of May normal) in parts of: Northland, Bay of Plenty, Taranaki, Kapiti Coast, Wellington, and Southland. In contrast, May rainfall was around 50 percent of normal in the Buller district. May rainfall was below normal (50-79 percent of May normal) for parts of Hawke's Bay and inland Canterbury. May rainfall was near normal elsewhere. As at 1 June, below normal soil moisture levels for the time of year were observed in Hawke's Bay and Wairarapa, as well as around the Queenstown Lakes district. Near normal soil moisture levels were evident elsewhere, except for Marlborough, Kaikoura Coast, coastal Otago, and coastal southern Canterbury, where soils were much wetter than usual for the time of year.


Mean temperatures for May were above average (0.5 to 1.2°C above the May average) across most of the central and eastern North Island. In general, May temperatures were near average throughout the remainder of the country (within 0.5°C of May average). Low temperatures were experienced throughout the country on May 28, with many locations recording their lowest May afternoon temperatures on record. The nation-wide average temperature in May 2013 was 11.1°C (0.4°C above the 1971-2010 May average, using NIWA's seven-station temperature series which begins in 1909).


Sunshine hours for May were above normal (110 to 124 percent of May normal) for the central North Island and the west coast of the South Island south of Franz Josef. Sunshine was well above normal (more than 125 percent of May normal) in Taumarunui. Sunshine hours were near normal (90-110 percent of May normal) for the remainder of the country except for Taranaki, where sunshine hours were below normal (75-90 percent of normal). Of the available, regularly reporting sunshine observation sites, the sunniest four centres so far in 2013 (January to May) are: Whakatane (1288 hours), New Plymouth (1272 hours), Blenheim (1162 hours) and Paraparaumu (1160 hours). 

Percentage of normal rainfall for May 2013.
End of month water balance in the pasture root zone for an average soil type where the available water capacity is taken to be 150 mm.
Departure from average air temperature for May 2013.