Dry and sunny for eastern parts of the country.
Rainfall
Rainfall was well below normal (< 50%) or below normal (50-79%) for eastern parts of New Zealand from Gisborne all the way south to North Otago. Rainfall
was well above normal (> 149%) or above normal (120-149%) for western parts of the South Island, the Southern Lakes,
southwestern and western parts of the North Island, and eastern Bay of Plenty. Soil MoistureAs of 1 June 2015, soil moisture levels were below normal for this time of year for East Cape, coastal Wairarapa,
southern Marlborough and eastern parts of Canterbury. It was especially dry about North Canterbury where soils were
considerably drier than normal for this time of year. SunshineMay sunshine was abundant for eastern parts of New Zealand including the eastern Bay of Plenty, Gisborne, Hawke’s Bay,
Wairarapa, Marlborough, Canterbury and Otago where May sunshine was typically above normal (110-125%) or well above
normal (> 125%). TemperatureMay temperatures were above average (+0.51°C to +1.20°C) for parts of Southland, Otago, Canterbury, Wairarapa, Whanganui
and Southern Taranaki. May temperatures were below average in isolated parts of central Hawke’s Bay and western Waikato
(-0.51°C to -1.20°C).
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Overview
May 2015 was a mixed bag across New Zealand as a whole, with bouts of heavy rainfall, severe frosts and snow occurring
in addition to record or near-record dry and sunny conditions in eastern parts of Canterbury. Overall, the month was
characterised by air pressures which were well below normal in the Tasman Sea, with below normal pressures extending
over New Zealand. This circulation pattern was accompanied by a westerly flow anomaly over New Zealand. This flow
anomaly was clearly reflected in the distribution of rainfall anomalies observed across New Zealand. Specifically,
rainfall was below normal (50-79% of the May normal) or well below normal (< 50% of the May normal) for many eastern areas of New Zealand including North Otago, Canterbury, Marlborough, Wairarapa
and Gisborne. It was especially dry in eastern parts of Canterbury, which was largely a result of the Southern Alps
consistently drawing out most moisture from rain-bearing air masses as they progressed eastward. In contrast, rainfall
was abundant for many western parts of New Zealand. Rainfall was either above normal (120-149% of May normal) or well
above normal (> 149% of the May normal) for western parts of the South Island, the Southern Lakes, southwestern and
western parts of the North Island, and eastern Bay of Plenty. Kapiti Coast was particularly hard hit by rain during the
month, with parts of the region receiving in excess of 300% of normal May rainfall. A considerable proportion of Kapiti
Coast’s rainfall fell during a single event, which resulted in significant flooding and record 1-day rainfall totals for
May (see Highlights and extreme events for further information). Rainfall was typically near normal (80-119% of the May normal) for remaining areas of the
country. The lack of rainfall for eastern parts of New Zealand has exacerbated concerns regarding soil moisture levels
in parts of New Zealand, but particularly in North Canterbury. As of 1 June 2015, soils were notably drier than normal
for East Cape, coastal Wairarapa, southern Marlborough and eastern parts of Canterbury. Elsewhere, soil moisture levels
were nearer to normal for this time of year, with the exception of northwestern Southland, where soils were wetter than
normal.
It was a sunny month for eastern parts of New Zealand, from eastern Bay of Plenty southwards to South Otago where May
sunshine was above normal (110-125% of the May normal) or well above normal (> 125% of the May normal). Inland parts
of the South Island, including the Southern Lakes, Central Otago and the Mackenzie Country also observed above normal or
well above normal May sunshine hours. Remaining parts of the country typically received near normal sunshine (90-109% of
the May normal).
Mean temperatures were much higher than average for much of the month across New Zealand. However, a polar outbreak in
late-May brought snowfall and severe frosts to many parts of the country, and lowered mean temperatures throughout New
Zealand for the month overall. Many parts of Southland, Otago, Canterbury, Wairarapa, Whanganui and Southern Taranaki
recorded above average temperatures (0.51-1.20°C above the May average). Temperatures were typically near average
(between -0.50°C to +0.50°C of the May average) for the remainder of the country. The exception was isolated parts of
central Hawke’s Bay and western Waikato where temperatures were below average (-0.51°C to -1.20°C below the May
average). The nation-wide average temperature in May 2015 was 11.2°C (0.4°C above the 1981-2010 May average from NIWA’s
seven station temperature series which begins in 1909) .
Further Highlights:
• The highest temperature was 27.0°C, observed at Waiau on 6 May.
•
• The lowest temperature was -9.0°C, observed at Hanmer Forest on 28 May.
•
• The highest 1-day rainfall was 190 mm, recorded at North Egmont on 6 May.
•
• The highest wind gust was 178 km/hr, observed at Cape Turnagain on 13 May.
•
• Of the six main centres in May 2015, Auckland was the warmest, Christchurch was the coolest and driest,
Wellington was the wettest, Tauranga was the sunniest and Dunedin was the cloudiest.
•
• Of the available, regularly reporting sunshine observation sites, the sunniest four centres so far in 2015 (1
January to 31 May) are: Whakatane (1200 hours), Blenheim (1182 hours), Waipara West (1173 hours) and Appleby (1173
hours).
•
For further information, please contact:
Mr Chris Brandolino
NIWA Forecaster – NIWA National Climate Centre
Tel. 09 375 6335, Mobile (027) 886 0014
Rainfall: Extremely dry in parts of Canterbury
May 2015 was a record or near-record dry month in seven New Zealand locations, with some parts of eastern mid-Canterbury
receiving as little as 5% of normal May rainfall. In contrast, it was a particularly wet month in Paraparaumu, which
observed its wettest May on record. In addition, Milford Sound recorded 896 mm of rainfall during May 2015; a remarkable
contrast to the 2 mm of rainfall which was recorded in Timaru over the same period of time.
Record or near-record May rainfall totals were recorded at:LocationRainfall total (mm)Percentage of normalYear records beganComments
High records or near-recordsParaparaumu2523031945HighestMotu28715019902nd-highestHawera18418819773rd-highestLow records or near-recordsAshburton7111909LowestLincoln6111881LowestOrari Estate471897LowestTimaru251881LowestMahia151419902nd-lowestHanmer Forest272919053rd-lowestWinchmore91419094th-lowest
Temperature: Above average for eastern and southern parts of the South Island
Relatively few locations observed record or near-record high mean temperatures for May, however this doesn’t reveal the
periods of record or near-record warmth and bitter cold that occurred from time to time (see Highlights and extreme events for further details). A small number of locations in eastern Canterbury observed record-or near record mean maximum air temperatures for
May, which may be primarily attributed to the foehn effect associated with the westerly flow anomaly observed across New
Zealand during the month. The nation-wide average temperature in May 2015 was 11.2°C (0.4°C above the 1981-2010 May
average from NIWA’s seven station temperature series which begins in 1909).
Record or near-record mean air temperatures for May were recorded at:LocationMean
air temp. (oC)Departure from normal (oC)Year records beganCommentsHigh records or near-recordsCheviot10.51.419822nd-highestLow records or near-recordsSecretary Island10.5-0.519854th-lowest
Record or near-record mean maximum air temperatures for May were recorded at:LocationMean maximum
air temp. (oC)Departure from normal (oC)Year records beganCommentsHigh records or near-recordsCheviot17.62.41982HighestChristchurch (Riccarton)17.73.118632nd-highestWaiau School16.92.319743rd-highestOrari Estate15.72.119723rd-highestKaikoura16.22.019634th-highestLincoln16.32.018814th-highestTimaru15.61.818854th-highestCampbell Island8.90.619914th-highestLow records or near-recordsSecretary Island12.7-0.919853rd-lowestTe Kuiti15.1-1.519594th-lowest
Record or near-record mean minimum air temperatures for May were recorded at:LocationMean minimum
air temp. (oC)Departure from normal (oC)Year records beganCommentsHigh records or near-recordsNgawi11.41.019723rd-highestLow records or near-recordsHicks Bay9.5-1.319694th-lowest
Sunshine: Very sunny for eastern parts of the country
May sunshine was plentiful for eastern parts of both the North Island and South Island, as well as inland parts of the
South Island. Blenheim and Cheviot observed their sunniest May on record, with five other South Island locations
observing near-record sunshine hours for the month. Of the available, regularly reporting sunshine observation sites,
the sunniest four centres so far in 2015 (1 January to 31 May) are: Whakatane (1200 hours), Blenheim (1182 hours),
Waipara West (1173 hours) and Appleby (1173 hours). It was a relatively cloudy month in New Plymouth compared to other
New Zealand centres. This has resulted in the city dropping from sunniest centre for the year to date at the end of
April 2015, to fifth-sunniest centre for the year to date at the end of May 2015.
Record or near-record May sunshine hours were recorded at:LocationSunshine hoursPercentage of normalYear records beganComments
High records or near-recordsBlenheim2141251947HighestCheviot1871551983HighestAshburton18314019302nd-highestLake Tekapo18512819282nd-highestQueenstown12414119303rd-highestWaipawa18313619454th-highestBalclutha12412919644th-highestLow records or near-recordsNone observed
May climate in the six main centres
May temperatures were largely near average in the main centres for this time of year. The exception was Christchurch,
where the mean temperature was above average. It was also very dry in Christchurch, with the city receiving just 29% of
normal May rainfall. In contrast, rainfall was above normal in Hamilton and Wellington, with the latter suffering
multiple flooding events during the month (see Highlights and extreme events section for further details). Of the six main centres in May 2015, Auckland was the warmest, Christchurch was the
coolest and driest, Wellington was the wettest, Tauranga was the sunniest and Dunedin was the cloudiest.
May 2015 main centre climate statistics:TemperatureLocationMean temp. (oC)Departure from normal (oC)CommentsAucklanda14.2+0.2Near averageTaurangab13.0-0.3Near averageHamiltonc11.5-0.1Near averageWellingtond12.2+0.5Near averageChristchurche9.6+0.6Above averageDunedinf9.8+0.5Near averageRainfallLocationRainfall (mm)% of normalCommentsAucklanda125116%Near normalTaurangab9586%Near normalHamiltonc153143%Above normalWellingtond155139%Above normalChristchurche1729%Well below normalDunedinf5787%Near normalSunshineLocationSunshine (hours)% of normalCommentsAucklanda13292%Near normalTaurangab177107%Near normalHamiltong142108%Near normalWellingtond12997%Near normalChristchurche173124%Above normalDunedinf117 108%Near normal
a Mangere b Tauranga Airport c Hamilton Airport d Kelburn e Christchurch Airport f Musselburgh g Ruakura
Highlights and extreme events
Rain and slips
On 6 May, torrential rain and flooding accompanied by strong northwest winds hit the West Coast of the South Island.
State Highway (SH) 6 at Haast Pass was closed due to a slip. Caution was advised between Ross and Haast on SH 6 due to
surface flooding and slips. SH 94 from Te Anau to Milford Sound was closed for a time due to flooding.
On 12 May, Wellington was affected by heavy rain, resulting in significant surface flooding in many parts of the city as
drains couldn’t cope with the sudden downpour. The rain also forced the cancellation of Victoria University’s graduation
parade.
On 14 May, torrential rain caused flooding in Kapiti, Porirua, and Lower Hutt areas. A slip blocked the road and rail
link between the Kapiti Coast and Wellington, closing SH 1 between Paekakariki and Pukerua Bay. SH 2 was closed at
Petone, and Paekakariki Hill Road was also closed. All commuter train services across the Wellington region were
cancelled and Wellington Railway Station was closed. Thousands of Kapiti and Hutt Valley residents were trapped in
Wellington city and forced to find alternative accommodation for the night. At least 20 homes were evacuated in Raumati
Beach, and a number of schools were closed throughout the region. The Hutt River burst its banks and flooded High Street
in Lower Hutt, threatening cars and stores. The Waikanae River also burst its banks, and floodwaters affected Tawa and
Porirua. A man swept under a bridge in floodwaters in Paraparaumu was helped to safety by bystanders, and police rescued
a cyclist who became trapped in floodwaters in the Waikanae River with a digger. An elderly man’s body was found near
his car which was underwater in Petone. On 15 May, some roads around the greater Wellington region remained closed due
to flooding, including Paekakariki Hill Road and Grays Road in Plimmerton. Surface flooding occurred in and around
Levin, where some houses were flooded and SH 57 was closed for a time.
On 24 May, torrential rain caused power outages in Auckland. Power was lost to almost 3000 homes in West Auckland,
northwest of Auckland, and Takapuna.
The highest 1-day rainfall was 190 mm, recorded at North Egmont on 6 May.
Record or near-record May extreme 1-day rainfall totals were recorded at:LocationExtreme 1-day rainfall
(mm)Date of extreme rainfallYear records beganCommentsParaparaumu11613th1951HighestWaione3415th19912nd-highestHawera6314th19772nd-highestWhakatane8823rd19524th-highestPalmerston North5714th19284th-highest
Temperatures
On 6 May northwest winds prevailed over the South Island. The associated foehn effect resulted in high temperatures for
this time of year throughout Canterbury. Daily maximum temperatures reached the mid-to-high-twenties in many locations.
Pre-dawn temperatures were very high in some parts too: between 4 a.m. and 5 a.m. Christchurch (Riccarton) and Winchmore
(near Ashburton) recorded a maximum temperature of 20.9°C and 21.1°C, respectively.
On 28 and 29 May, low morning temperatures were experienced throughout the country, with severe frosts in some parts.
Clear skies at night enabled considerable radiative cooling to occur, and a number of New Zealand locations observed
record or near-record low temperatures for May.
The highest daily maximum temperature for the country was 27.0°C, observed at Waiau School on 6 May. This was followed
by 26.8°C at Rangiora on 6 May, and 26.7°C at Christchurch (Riccarton) on 6 May.
The lowest daily minimum temperature for the country was -9.0°C, observed at Hanmer Forest on 28 May. This was followed
by -8.6°C at Pukaki Aerodrome on 29 May, and -8.1°C at Ranfurly on 29 May.
Record or near-record daily maximum air temperatures for May were recorded at: LocationExtreme maximum (°C)Date of extreme temperatureYear records beganComments
High records or near-recordsAppleby25.07th1932HighestHanmer Forest24.76th1906HighestCheviot26.56th1982HighestWaiau School27.06th1974Equal highestAuckland (Airport)24.47th19592nd-highestDannevirke23.87th19512nd-highestWaione25.17th19912nd-highestCastlepoint22.37th19722nd-highestPuysegur Point19.85th19782nd-highestLe Bons Bay22.07th19842nd-highestOrari Estate25.56th19722nd-highestDunedin (Musselburgh)24.66th19472nd-highestTakapau Plains23.57th1962Equal 2nd-highestStratford20.28th1960Equal 2nd-highestNugget Point20.46th1970Equal 2nd-highestAuckland (Whenuapai)23.57th19453rd-highestWhatawhata22.57th19523rd-highestWaipawa23.47th19453rd-highestKaikoura25.57th19633rd-highestChristchurch (Riccarton)26.76th18633rd-highestMokohinau20.56th1994Equal 3rd-highestWaipara West25.96th19734th-highestChristchurch (Airport)26.66th18634th-highestCampbell Island13.26th19914th-highestBlenheim23.67th1932Equal 4th-highestLow records or near-recordsMotueka7.830th1972LowestTakaka10.330th1978Equal 3rd-lowestTurangi8.325th19684th-lowestWaione9.625th19934th-lowestMahia9.725th19904th-lowestSecretary Island8.425th1989Equal 4th-lowest
Record or near-record daily minimum air temperatures for May were recorded at:LocationExtreme minimum (°C)Date of extreme temperatureYear records beganComments
High records or near-recordsTe Puke17.28th1973HighestWhatawhata17.98th1952HighestNew Plymouth17.47th1944HighestMasterton17.27th1992HighestWairoa18.28th1972HighestStratford15.28th1972HighestHawera16.17th1977HighestFarewell Spit16.37th1972HighestReefton16.07th1972HighestPuysegur Point16.46th1978HighestBlenheim18.37th1972HighestKaikoura16.07th1972HighestCheviot17.57th1982HighestWaipara West19.77th1973HighestLe Bons Bay15.47th1984HighestCampbell Island10.46th1991HighestParaparaumu16.57th1972Equal highestArthurs Pass11.07th1973Equal highestCulverden16.87th1930Equal highestTakapau Plains15.48th19722nd-highestDannevirke16.27th19512nd-highestWaione16.77th19932nd-highestMartinborough16.57th19862nd-highestPalmerston North16.37th19402nd-highestWallaceville (Upper Hutt)16.17th19722nd-highestWanganui17.87th19722nd-highestGreymouth15.37th19722nd-highestSecretary Island14.56th19882nd-highestNelson16.67th19432nd-highestNgawi17.87th1972Equal 2nd-highestMahia16.58th1990Equal 2nd-highestWellington (Airport)16.97th1972Equal 2nd-highestTakaka15.47th19783rd-highestHanmer Forest15.07th19723rd-highestWaiau School15.37th19743rd-highestRanfurly11.07th19753rd-highestInvercargill12.56th19053rd-highestHamilton16.88th1946Equal 3rd-highestCastlepoint17.08th1972Equal 3rd-highestGisborne17.88th1940Equal 3rd-highestWestport15.07th1966Equal 3rd-highestWhitianga17.48th19714th-highestWhakatane17.18th19754th-highestRotorua15.78th19724th-highestMotu13.88th19904th-highestKaikohe16.67th1973Equal 4th-highestPort Taharoa16.97th1974Equal 4th-highestOhakune13.08th1972Equal 4th-highestHokitika14.97th1866Equal 4th-highestLow records or near-recordsTurangi-5.429th1968LowestWaione-6.129th1991LowestMahia3.726th1990LowestWallaceville (Upper Hutt)-4.926th1939LowestAppleby-7.029th1932LowestBlenheim-5.126th1932LowestCheviot-6.329th1982LowestChristchurch (Airport)-6.429th1863LowestTe Kuiti-3.129th1959Equal lowestLe Bons Bay0.225th1984Equal lowestHanmer Forest-9.028th19062nd-lowestTaumarunui-4.328th19473rd-lowestWinchmore-6.729th1928Equal 3rd-lowestRanfurly-8.129th1975Equal 3rd-lowestKaitaia4.528th19854th-lowestMotu-5.329th19904th-lowestMasterton-3.326th19924th-lowestTakapau Plains-2.730th19624th-lowestCastlepoint2.925th19724th-lowestWairoa-0.330th19644th-lowestWaiau School-6.028th19744th-lowestAshburton-6.529th19284th-lowestOrari Estate-4.329th19724th-lowestDunedin (Airport)-7.229th19624th-lowestNugget Point-0.225th1970Equal 4th-lowest
Wind
On 6 May, extra caution was required by motorists travelling on the Desert Road (SH 1), SH 2 at Rimutaka Hill, and SH 73
near Arthurs Pass due to strong winds. Overnight on 6 May, over 1000 homes in Wellington’s northern suburbs lost power
due to the wind. On 7 and 8 May, wind warnings remained in place for motorists travelling on SH 73 near Arthurs Pass, SH
7 at Lewis Pass, and SH 2 at Rimutaka Hill.
In the early morning of 12 May, a mini tornado caused damage in Urenui, north of New Plymouth. The roof of a petrol
station was damaged as well as fences, trees, and guttering.
On 14 May, a tornado ripped through Mt Maunganui, damaging homes and buildings, pulling down fences and sending
trampolines flying. About 20 homes had roofs lifted and 11 had significant damage. Part of the roof and grandstand of
Baypark Stadium was severely damaged. Earlier, a reported tornado ripped the roof off a house and damaged at least three
more properties at Coopers Beach in the Far North.
On 15 May, a Cessna plane flipped on the runway at Tauranga airport due to high winds. Strong winds lasting about five
minutes battered Tauranga Girls’ College, damaging shade sails and table umbrellas, as well as scattering outdoor
furniture.
On 20 and 21 May, strong wind warnings were present for SH 2 at Rimutaka Hill, with caution advised for motorists
travelling there.
On 24 and 25 May, strong southwest winds affected much of the country, especially in the lower South Island. Numerous
ferry services on Cook Strait were cancelled or delayed due to strong winds and associated large swells. Interislander sailings remained affected by the rough conditions until 27 May.
The highest wind gust was 178 km/hr, observed at Cape Turnagain on 13 May.
Record or near-record May extreme wind gusts were recorded at:LocationExtreme wind gust (km/hr)Date of extreme gustYear records beganCommentsWhakatane10012th19742nd-highestHawera8925th19862nd-highestPukekohe6915th1986Equal 2nd-highestNorth Shore, Auckland6915th19943rd-highestLyttelton Harbour9625th19803rd-highestOamaru8724th19843rd-highestRotorua9115th1972Equal 3rd-highestHamilton7625th1991Equal 3rd-highestKaikoura12822nd19724th-highestAshburton986th19704th-highestTaupo8225th1982Equal 4th-highestMotu8212th1991Equal 4th-highest
Snow and ice
On 12 May, light snow was observed in the area around Naseby, Central Otago.
On 14 May, a road snowfall warning was in place for SH 94 from Te Anau to Milford Sound, with snow falling near the
Homer Tunnel. All vehicles were required to carry chains and no towing was allowed.
On 15 May, SH 94 from Te Anau to Milford Sound was closed due to snow.
On 21 and 22 May, a road snowfall warning was in place for SH 94 from Te Anau to Milford Sound, and vehicles were
required to carry chains.
On 24 and 25 May, a cold southerly blast hit the country and caused snowfall throughout most of Otago, Southland, as
well as the mountain passes and relatively high-elevation settlements in Canterbury. Up to 30 cm of snow was reported in
Arrowtown, with 10-25 cm reported in Queenstown, Cromwell and Wanaka. Snow briefly fell to sea level in Dunedin but
didn’t settle at that elevation, however up to 10 cm was reported in the hill suburbs. Snow fell down to 300 m above sea
level in Hawkes Bay, and heavier falls were reported on the Napier-Taupo Road. Roads closed by snow included: SH 75 from
Little River to Barrys Bay, SH 58 from Alexandra to Ranfurly, SH 6 from Cromwell to Frankton, SH 1 from Pine Hill to
Waitati, SH 93 from Clinton to Mataura, SH 85 from Kyeburn to Palmerston, and SH 87 from Kyeburn to Outram. Many roads
required chains to be worn and towing was prohibited. Caution was advised at SH 2 on Rimutaka Hill due to snow and ice.
All schools in Wanaka were closed, and many schools around Dunedin started later in the day. Flights were delayed in
Queenstown as crews cleared the runway of snow.
On 26 and 27 May, many roads in Otago and Southland were still affected by snow and ice, and caution was advised to
motorists travelling in these areas.
Lightning and hail
On 12 May, thousands of lightning strikes were recorded over the country (mainly in the west of both Islands). The
thunderstorms were generated by atmospheric instability associated with fronts within a disturbed northwesterly flow.
On 25 May, a lightning strike caused power to be knocked out to some homes in Dunedin.
Cloud and fog
On 4 May, hundreds of people were stranded due to fog cancelling and delaying flights into and out of Christchurch
airport.
On 11 May, heavy fog blanketed the Waikato with motorists urged to take extra caution on the roads.
ENDS