Climate extremes create records

Weather records were broken around Otago in September - not due to a lack of rainfall as had been feared but instead because of extreme temperatures.

Nationally, record cold temperatures were experienced early in the month, when a large anticyclone became slow moving across the country, and then extreme northwesterly winds affected the South Island on the 14th, bringing record-high temperatures, National Institute of Water and Atmospheric Research's national climate summary for September says.

A record extreme daily cold temperature was experienced at Dunedin airport (-4.7degC, the lowest since 1947) on the 5th, while a national high for September was recorded in Alexandra on the 14th - the 29degC temperature was also the highest for the town since records began in 1928.

Oamaru experienced its third-lowest extreme daily temperature of -4degC, also on the 5th, and Queenstown -3.8degC on the 4th, its equal third-lowest.

Dunedin airport also experienced its lowest mean temperature (since records began in 1947) for September of 2.7degC.

Overall, the city's average temperature was 9.9degC, 0.6degC higher than normal. The national average was 10.6degC, 0.3degC above the long-term September average.

Extreme daily maximum temperatures were also recorded on the 14th in Cromwell, which experienced its highest September reading of 26degC, Oamaru (its second-highest, 26.4degC), Dunedin at Musselburgh (its second-highest, 25.4degC) and Queenstown (its fourth-highest, 23.3degC).

Earlier in September, coastal Otago had experienced less than half its normal rainfall but, thanks to a deep, wintry low that crossed New Zealand on the 24th, Dunedin received 46mm, 87% of its normal rainfall by the end of the month.

Elsewhere in the region, rainfall levels did not reach record levels for either high or low rainfall although parts of inland Otago experienced less than 50% of their usual rainfall and the area around Oamaru received between 120% and 150% of normal, the report said.

Dunedin hydrologist Dave Stewart said Otago had experienced a significant dry patch from July through to September so the easterly rain came at the right time.

"It filled the lowland rivers and gave the ground much-needed moisture."

The rain and recent light snow on the hills would give the region a bit of "resilience" as it moved through to summer, he said.

- rebecca.fox@odt.co.nz

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