NIWA

Climate Summary for October 2009

3 November 2009

Coldest October in over half a century

Temperature: The coldest October in 64 years, with all-time record low October temperatures in many areas. Exceptionally late snowfalls. Record low October temperatures were recorded on the 4th/5th in most North Island locations, and on the 9th at many South Island sites.
Rainfall: Well above normal rainfall in the east of the North Island, as well as in Wellington, Marlborough and parts of Canterbury. Very dry on the West Coast of the South Island.
Sunshine: Extremely sunny on the West Coast of the South Island.

Record or near-record low October temperatures were experienced in many locations, with temperatures more than 2.0°C below average throughout eastern and alpine areas of the South Island, as well as in the lower half of the North Island. Temperatures were below average (between 0.5°C and 1.2°C below average) elsewhere. Overall for New Zealand, it was the coldest October in 64 years (since 1945), with a national average temperature of 10.6°C (1.4°C below the long-term October average). Such a cold October has occurred only four times in the past 100 years. Record low October temperatures were recorded on the 4th/5th in most North Island locations, and on the 9th at many South Island sites.

Well above normal October rainfall (above 150 percent of normal) was experienced across the East Coast of the North Island, as well as Wellington, Marlborough and Canterbury (north of about Ashburton). Rainfall was near-record (and more than 200 percent of normal) in parts of Hawkes Bay, Gisborne and the Tararua District. Rainfall was also above normal (between 120 and 150 percent of normal) in Manawatu-Wanganui, Waikato and the Bay of Plenty. Rainfall totals were near normal (between 80 and 120 percent of normal) in the Tasman District, central Otago, Auckland, Taranaki and western parts of Northland. In contrast, it was very dry on the West Coast and in Fiordland, with only about half of normal October rainfall recorded there.

October sunshine totals were well above normal (more than 125 percent of normal) on the West Coast and in Fiordland; in contrast, sunshine totals were below normal (between 75 and 90 percent of normal) for Taranaki, Wellington and the Wairarapa. Elsewhere, sunshine totals were in the near normal range.

Unseasonable snowfalls characterised October 2009. An exceptionally heavy snow event on the 4th/5th in the Hawkes Bay and Central North Island was estimated to be the worst in October since 1967, stranding hundreds of travellers, closing roads, and resulting in heavy lambing losses. Many locations in the North Island experienced record low October temperatures on the 5th. Snowfall was also observed in Taranaki, Waikato and Rotorua on the 6th, for the first time in about 30 years around Rotorua. Snowfall also affected Otago and Canterbury on the 8th/9th, with many sites observing record low October temperatures on the 9th.

During October 2009, lower than normal pressures and frequent southeasterly winds affected New Zealand, leading to the low temperatures around the country. Southeasterlies also led to the sunny and dry conditions experienced on the west coast of the South Island, as the Southern Alps provided shelter from the wind.

Further Highlights:

The highest temperature was 24.3°C recorded at Whangarei on the 17th (4th highest in October). The lowest temperature of -5.5 °C was recorded at Ranfurly on the 5th (not a record).
The highest 1-day rainfall was 89 mm, recorded at Motu, Gisborne, on the 4th (not a record).
The highest wind gust was 148 km/hr, recorded at Stewart Island on the 21st (not a record).
Of the six main centres, Tauranga was the warmest, Wellington the wettest, Dunedin the coolest and driest, and Christchurch the sunniest.