National Climate Summary

National Climate Summary – May 2012:  Dry over the South Island; generally sunny & cool

• Rainfall: Extremely dry in Canterbury, and generally dry elsewhere in the South Island.
• Sunshine: Extremely sunny for western regions, and generally above normal sunshine elsewhere.  Closer to normal sunshine for Canterbury, Gisborne, and Nelson.
• Temperatures: Below average for much of the North Island, as well as the north and east of the South Island.  Near average in the southwest of the country.
• Soils: Drier than normal in Canterbury and Nelson, as well as the Tararua District and around Palmerston North.

May was characterised by higher pressures than normal to the southeast of the country.  Lower pressures than usual were observed near Tasmania and also to the east of the North Island.  This pressure pattern resulted in more easterly quarter winds than usual over New Zealand.

It was an extremely dry May for Canterbury, with less than a quarter of normal May rainfall recorded – and it was generally dry elsewhere in the South Island.  It was the 2nd-driest May on record for Christchurch.  Rainfall was around half of May normal in Nelson and Marlborough, and across much of Westland and Otago.  In Fiordland and for the alpine districts, rainfall ranged between 50 and 80 percent of May normal.  Rainfall totals were near normal in Southland, as well as across much of the north and west of the North Island.  In contrast, northern Hawkes Bay and coastal Bay of Plenty experienced a wet May, whilst Gisborne, southern Hawkes Bay, and much of the Tararua District recorded below normal rainfalls.  At the end of May, soils were much drier than normal for the time of year in Canterbury and Nelson, as well as in the Tararua District and around Palmerston North.  Elsewhere, soil moisture levels were generally near normal.

May was an extremely sunny month in the west of both islands.  Well above normal sunshine totals were observed in western regions between Hamilton and the Kapiti Coast, as well as Westland, Fiordland and Southland.  It was the sunniest May on record for New Plymouth and Queenstown – in over 80 years of record in the case of Queenstown.  Sunshine totals were also above normal in most other parts of the country.  The exceptions were Canterbury, Gisborne and Nelson, which experienced closer to normal sunshine totals.

Mean temperatures for May were generally below average across much of the North Island, as well as the north and east of the South Island.  Temperatures were near average (within 0.5°C of the May average) in the southwest of the country (Southland, Fiordland, and southern Westland), as well as locally around Christchurch, and in parts of Auckland and Northland and coastal Bay of Plenty.  The nation-wide average temperature in May was 10.3°C (0.4°C below the 1971–2000 May average), using NIWA’s seven-station temperature series which begins in 1909.

Further Highlights:

• The highest temperature experienced was 23.4°C, recorded at Whangarei on 9 May.
• The lowest temperature experienced was -8.1°C, recorded at Ranfurly on 20 May.
• The highest 1-day rainfall experienced was 207 mm, recorded at North Egmont on 27 May.
• The highest gust recorded was 139km/h, recorded at Cape Reinga on 8 May.
• Of the six main centres, Auckland was the warmest, Tauranga the wettest but also the sunniest, Christchurch the coolest and driest, and Dunedin the cloudiest.