September weather set both heat, rain records

Taking advantage of the warm weather last month, Ricky Allen runs one of his trotters along Katiki Beach. PHOTO: STEPHEN JAQUIERY

Records tumbled in a tumultuous September, which brought heat and heavy rain to the South.

Niwa climate scientist Gregor Macara said New Zealand’s warmest September on record was a month of two halves for Otago and Southland.

"It was clearly a very warm month. Despite the distinct period of it being relatively dry to start and then quite wet at the end, the common theme was that overall it was pretty warm everywhere."

A long dry spell in Central Otago started in August and continued through until September 20.

Then, the skies opened and rain fell.

One storm delivered the bulk of the rain for the month, breaking single-day records at nine southern sites.

When the rain arrived, the moisture was carried in on light winds from the northwest, but the storm ended with the wind shifting to the southwest, bringing in cold air that dragged temperatures down, Mr Macara said.

Clyde only reached 5.5°C for a daytime high on September 22, setting the country’s only low record for the month.

The highest one-day rainfall in New Zealand last month was 234mm at Milford Sound on September 20.

However, over the next two days, a deluge flooded parts of the south and a State of Emergency was declared in Southland and Queenstown.

Stormwater and wastewater systems in Gore and Mataura became overwhelmed and widespread surface flooding threatened homes and businesses.

Inundated stormwater drains reportedly became contaminated with sewage in Winton, Lumsden and Nightcaps.

In Queenstown, 68 properties were evacuated due to flooding and debris, Mr Macara’s monthly climate summary said.

Tara Hills, near Omarama, received 166mm of rain last month, or 441% of its normal amount.

It was the second highest amount of rain in a September since records began in 1948.

Across New Zealand, 14 places set record high September average temperatures.

Windsor, Ranfurly, Dunedin, Te Anau and Balclutha all had their third warmest Septembers.

Waimate and Gore recorded their fourth warmest Septembers.

All were more than 1°C warmer than their historic averages for the month.

On September 20, before the rain arrived in Southland and Otago, Oban, on Stewart Island, recorded a daily high of 23.5°C — a full 6°C higher than its normal daily maximum temperature in February.

Also on September 20, Timaru reached 28.9°C, its highest September temperature since records began in 1885 and the fifth-highest September temperature on record.

Of the six main centres in September, Dunedin was the driest, Mr Macara’s summary said.