May 2006

• Rainfall: Well above average in Northland, Auckland, and Canterbury; well below average parts of Otago
• Temperature: Above average in northern and eastern parts of the North Island; below average in the east of the South Island
• Sunshine: Very sunny in North Westland and Southland; rather cloudy in Gisborne and parts of Canterbury

May was very wet, with about 200 percent (twice) of normal rainfall, in parts of Northland and Auckland, and in many coastal areas of Canterbury. The month’s weather was rather unsettled in these regions, including Northland, Coromandel, and Bay of Plenty, with six to eight more wet-days (days with rainfall totalling at least 1.0 mm) than average in many locations. Soils in many parts of the country are now saturated. In contrast, May rainfall was less than 50 percent (half) of normal in Central and East Otago. May was warmer than average in much of the north and east of the North Island, and Nelson and the west of the South Island, but cooler than average in parts of Wairarapa, South Canterbury, Otago and Southland. The national average temperature of 11.0 °C was 0.3 °C above the 1971-2000 normal. This was the lowest for May since 1996. May was much sunnier than normal in North Westland and Southland. However, sunshine hours were well below normal in Gisborne and coastal areas of Canterbury. Troughs of low pressure were more frequent than average over the north of the North Island during May. This pattern resulted in frequent easterly winds over the South Island.

Other Highlights:

• The highest temperature recorded during May 2006 was 23.6 °C recorded in Henderson, Auckland on the 1st. The lowest temperature for the month was -5.9 °C at Lake Tekapo on the 15th.
• On 8 May, lightning struck a tree in Auckland, shattering at least 16 nearby windows, burning out electrical appliances, and resulting in a localised power outage.
• On 11 May, a small tornado lifted half a roof off a Ruawai (Kaipara) house.
• The highest wind gust recorded during May 2006 was 120 km/h. This was from the south-southwest at Castlepoint on the 15th, and from the northeast at Cape Reinga on the 26th.
• Wintry conditions occurred with a cold southerly outbreak during 14-15 May. In Canterbury, snowfall closed Burkes Pass with several vehicles stranded. Snowfall also occurred between Te Anau and Milford, as well as the Cashmere Hills. In the North Island, snowfall closed the Desert Road. The same event produced gale force southerlies with high seas in Cook Strait, and hail in parts of Auckland.
• High rainfall events were frequent in May, occurring in various districts on 2, 6, 12-13, 20-22, and 25-26 May. Substantial surface flooding occurred in Silverdale, north of Auckland on 6 May, in parts of Christchurch on 12 May, and in Tasman on 22 May.
• Dunedin was the driest, Auckland the wettest, Hamilton the sunniest, and Christchurch the coldest of the main centres. Rainfall was above average in Auckland and Christchurch, near average in Hamilton and Wellington, and well below average in Dunedin. Temperatures were near average in Christchurch and Dunedin, and above average in the three other main centres. Sunshine hours were above average in Hamilton, near average in Auckland, and Dunedin, and below average in the two other main centres.

Rainfall

Rainfall was about 200 percent (twice) of normal in parts of Northland and Auckland, and in many coastal areas of Canterbury. Rainfall was also above normal in parts of Bay of Plenty, coastal Wairarapa, Nelson, and North Otago. In contrast, May rainfall totals were 50 percent (half) or less of normal in Central and East Otago, and also below normal in South Westland, Fiordland, and coastal Southland.

Temperature

Mean temperatures were 0.5 °C or more above average in parts of Auckland, Bay of Plenty, Waikato, Gisborne, Hawke’s Bay, Buller, Westland, Fiordland, and Nelson. In contrast, they were at least 0.5 °C below average in parts of Wairarapa, South Canterbury, Otago and Southland.

Sunshine

Sunshine hours and/or solar radiation were at least 120 percent of normal in North Westland and Southland. In contrast, they were less than 80 percent of normal in Gisborne and coastal areas of Canterbury, and less than 90 percent of normal in Northland and West Otago,

Full report

• Full details of the May 2006 Climate Summary

For further information, please contact:

Dr Jim Salinger – Principal Scientist, Climate
NIWA National Climate Centre – Auckland
Phone +64 9 375 2053
[email protected]

Stuart Burgess – Climatologist
NIWA National Climate Centre – Wellington
Phone +64 4 386 0569
[email protected]

Geoff Baird – Communications Manager
Phone +64 4 386 0543
[email protected]

Acknowledgement of NIWA as the source is required.