Summer 2015

A persistently dry summer for all.

Rainfall 

Rainfall was below normal (50-79% of normal summer rain) for much of New Zealand during summer. Areas that were particularly affected by the dryness include eastern Otago, Canterbury, Marlborough, Wairarapa and parts of the Waikato where well below normal rainfall (<50% of normal summer rain) was observed. The district of Whangarei, coastal Bay of Plenty and southwestern Southland were the only areas of New Zealand to receive near normal rainfall (80-119% of normal summer rain).

Soil moisture

As of 1 March 2015, soil moisture levels were below normal for the time of year for extensive areas of New Zealand, with the exception of Central Otago and northern Southland.

Temperature

Summer temperatures as a whole were above average (0.51°C to 1.20°C) for the majority of the South Island with the exception of Marlborough and coastal parts of Canterbury and Otago where temperatures were in the near average range (-0.50°C to +0.50°C). In the North Island, temperatures were above average for parts of Auckland, Waikato and the Bay of Plenty as well coastal portions of Taranaki and Manawatu-Whanganui. Summer temperatures were in the near average range for the remainder of the North Island.

Sunshine

Summer sunshine was plentiful for much of the South Island as well as Taranaki, Manawatu-Whanganui and the Hawke’s Bay where above normal sunshine hours (110-125%) were recorded. Sunshine over the north of the North Island and the Wellington, Tasman, Nelson and Marlborough regions was in the near normal range (90-109%).

Overview

During December and January, higher than normal pressures were centred over the Chathams and extended over New Zealand bringing about an anomalous northeasterly airflow. This circulation pattern was characteristic of the summer period of 2014-2015 as a whole despite February bringing slightly more southwesterlies than normal.

The predominance of anticyclones (highs) during summer was reflected in the seasonal rainfall totals with almost the entirety of the country receiving below normal (50-79%) or well below normal (< 50%) rainfall. As a result of this widespread dryness several locations around New Zealand from north to south observed record or near-record low summer rainfall totals. Areas particularly affected by the dryness include eastern Otago, Canterbury and Marlborough where rainfall totals from December to February were consistently well below normal (<50%). Consequently a medium-scale drought event was declared on 12 February for these regions. The Wairarapa has similarly been impacted by the prevalence of dry conditions across all three summer months and is currently under “Watch” by MPI for drought development. The district of Whangarei, coastal Bay of Plenty and southwestern Southland were the only areas of New Zealand to receive near normal rainfall (80-119% of normal summer rain).

Soil moistures around the country have mirrored the trend in summer rainfall and rapidly depleted as we progressed from December to February. As of 1 March 2015, soil moisture levels remain below normal for the time of year for extensive areas of New Zealand, with the exception of Central Otago district and northern Southland.

Temperature-wise, summer got off to a cool start during the first half of December but quickly ramped up during the second half of December and into the particularly warm month of January. National temperatures eased back to near average during February as the frequent northeasterlies experienced during the first two summer months abated and weak southwesterlies ensued. For summer as a whole, temperatures were above average (0.51°C to 1.20°C) for the majority of the South Island with the exception of Marlborough and coastal parts of Canterbury and Otago where temperatures were in the near average range (-0.50°C to +0.50°C). In the North Island, temperatures were above average for parts of Auckland, Waikato and the Bay of Plenty as well coastal portions of Taranaki and Manawatu-Whanganui. Summer temperatures were in the near average range for the remainder of the North Island. The nation-wide average temperature in summer 2014-2015 was 17.1°C (0.5°C above the 1981-2010 summer average, using NIWA’s seven-station temperature series which begins in 1909)[1]

Further Highlights:

  • The highest temperature was 36.4°C, observed at Timaru on 16 January.
  • The lowest temperature was -2.4°C, observed at Pukaki on 2 December.
  • The highest 1-day rainfall was 194 mm, recorded at North Egmont 1 February. 
  • The highest wind gust was 178km/hr, observed at Cape Turnagain on 7 December.
  • Of the six main centres in summer 2014-2015, Auckland was the warmest, Dunedin was the coolest, Christchurch was the driest, Hamilton was the cloudiest and Tauranga was the sunniest and wettest (wettest in a relative sense as rainfall was below normal for all of the six main centres).

Download the full report:

Seasonal Climate Summary - Summer 2015

For further information, please contact:

Mr Chris Brandolino
NIWA Forecaster – NIWA National Climate Centre
Tel. (09) 375 6335
Mobile (027) 866 0014