Parts of Otago and Southland were on track to record one of their warmer Mays in recent history — that was until a bit of snow and some hard frosts introduced themselves near the end of the month.
Niwa climate scientist Gregor Macara said temperatures were above average or well above average for many parts of the country, but southern and central parts of Otago and Southland were near average.
"This was largely due to the persistence of clear skies associated with high air pressures, and prevalence of drier than normal soils, enabling enhanced radiative warming and cooling ... day and night."
Twenty-nine locations across the country observed record or near-record high daily maximum temperatures.
Otago featured widely among nine locations which observed record or near-record low daily minimum temperatures.
On May 18, snow fell to low elevations over much of the South Island, particularly in Southland, forcing the closure of the Milford Road (SH94) and causing driving difficulties across Otago and Southland.
But it was not until May 26 and 27, when severe frosts covered many South Island areas, that temperature records started tumbling, he said.
Most notable was Tara Hills (Omarama), which recorded -10.8degC on May 27. It was the area’s coldest May temperature since records began in 1949, and New Zealand’s coldest May temperature since 2001, -10.9degC in Ophir.
Middlemarch also recorded its lowest May temperature (-10.1degC) and Dunedin Airport recorded its lowest-equal (-8.8degC) temperature.
Balclutha recorded its second-lowest (-5.7degC) since records began in 1964, and Clyde recorded its third lowest (-7.8degC) since 1978.
Ranfurly’s -9.3degC on May 26 was the third-equal lowest May temperature since records began in 1897.
It was so cold on the Taieri on May 27, that Dunedin Airport’s maximum temperature on the day was just 3.2degC, which was the location’s lowest daily maximum air temperature for May on record.
Top May temperature of 28.3degC was in Rangiora on May 11.
An exceptionally heavy rainfall event over the final three days of the month caused severe flooding in Canterbury.
For the month overall, rainfall was well above normal for much of Canterbury, where many areas observed at least twice the normal rainfall for May, he said.
Rainfall was also above normal for southern and Central Otago, and central and northern Southland, but it was below normal for coastal parts of the South Island from Invercargill to Oamaru.
Despite the rainfall at the end of May, drier than normal soils remain prominent in much of Otago and eastern Southland.
