A warm and dry finish to winter
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Temperature |
It was New Zealand’s fourth-warmest August on record. Temperatures were above average (0.51°C to 1.20°C above average) or well above average (>1.20°C above average) for most of the country. |
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Rainfall |
It was a particularly dry month for eastern and inland parts of Canterbury and North Otago, where less than 20% of normal August rainfall was recorded. Rainfall was below normal (50-79% of normal) or well below normal (<50% of normal) in parts of almost every region. Rainfall was above normal (120-149% of normal) or well above normal (>149%) in Northland and northern Auckland. |
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Soil Moisture |
At the end of the month, soil moisture levels were lower than normal in eastern parts of the South Island, and southern parts of the North Island. Soils were considerably drier than normal in eastern parts of south Canterbury and north Otago. Soil moisture levels were typically near normal for most remaining parts of New Zealand. |
Overview
August 2020 was characterised by higher than normal mean sea level pressure (MSLP) to the east of New Zealand, and lower than normal MSLP to the northwest of the country. This set up resulted in a northeast airflow anomaly (i.e. more northeasterly winds than normal), particularly in the North Island. The prevailing northeast winds resulted in warmer than usual temperatures for much of New Zealand. Overall, the nationwide average temperature in August 2020 was 10.1°C. This was 1.2°C above the 1981-2010 August average, making it New Zealand’s fourth-warmest August since NIWA’s seven station temperature series began in 1909. It has now been 43 consecutive months since New Zealand’s nationwide average temperature was below average. Temperatures were above average (0.51°C to 1.20°C above average) or well above average (>1.20°C above average) for most of the country. The only exceptions were parts of inland Wairarapa, Hawke’s Bay and the Central Plateau where temperatures were near average (within 0.50°C of average).
It was a dry finish to winter for most of the country, with parts of almost every region observing below normal (50% to 79% of normal) or well below normal (<50% of normal) rainfall. The exception was Northland and northern parts of Auckland, where rainfall was above normal (120% to 149% of normal) or well above normal (>149% of normal). It was a particularly dry month for eastern and inland parts of Canterbury and North Otago, where less than 20% of normal August rainfall was recorded.
The combination of relatively warm and dry weather meant a lack of natural snowfall for many mountainous areas of the country. Towards the end of the month, snow depth was approximately half of usual at several locations along the Southern Alps (based on approximately 10 years of snow depth data beginning in 2010). See Highlights and Extreme Events section for further details. Sea surface temperatures surrounding New Zealand were higher than normal by the end of the month, and this likely contributed to the warm air temperatures observed during the month. Overall, there were relatively few episodes of unsettled weather events during August. The benign climate pattern may be partly attributed to the polar jet stream, which was weaker than normal in the New Zealand region.
Further highlights
- The highest temperature was 25.1°C, observed at Timaru on 30 August.
- The lowest temperature was -8.2°C, observed at Pukaki Airport on 15 August.
- The highest 1-day rainfall was 79 mm, recorded at Milford Sound on 31 August.
- The highest wind gust was 187 km/h, observed at Cape Turnagain on 29 August.
- Of the six main centres in August 2020, Auckland was the warmest and wettest, Tauranga was the sunniest, Christchurch was the coldest and driest, and Dunedin was the least sunny.
- Of the available, regularly reporting sunshine observation sites, the sunniest four regions in 2020 so far are Bay of Plenty (1769 hours), Wider Nelson (1726 hours), Taranaki (1707 hours), and Marlborough (1679 hours).
