An average summer despite heavy rainfall

If you thought the past summer was cold and wet, you are half right.

Niwa’s Summer 2020-21 review showed rainfall was near normal for most of the South Island, but it was a particularly wet season for parts of central Otago and north Otago, partly due to heavy rainfall occurring over several days in early January.

Climate scientist Gregor Macara said Oamaru received 261mm, which was equivalent to 55% of its normal annual rainfall.

In early January, Islay Downs (Otago) received its highest one-day extreme rainfall since records began in 1969, Powder Creek (east Otago) and Clyde received their second highest, Roxburgh recorded its third highest, and Ranfurly, Ophir and Lee Flat recorded their fourth highest.

Between 150 and 200 holidaymakers had to be evacuated when the Otematata River burst its banks, another 200 people attending the Whare Flat Folk Festival (near Dunedin) were stranded because of rising water levels in the Silver Stream, and the Patearoa bridge was damaged and the water supply was shut down by flooding.

Middlemarch residents were also affected by flooding, and many roads across the region were closed due to flooding and slips.

The highest one-day rainfall was 132mm, recorded at Arthurs Pass on January 19.

However, those who thought it was a cold summer can take solace
from the glowing Niwa data which showed that temperatures were above average for the Otago region as a whole.

Mr Macara said summer temperatures were near average for the rest of the country, and no locations observed record or near-record mean temperatures for the season.

"This is in stark contrast to the last several summers, which produced numerous record or near-record mean temperatures.

"It is likely that clearer than usual skies combined with drier than usual soils contributed to this temperature pattern, by enabling enhanced radiative heating and cooling during the day and night."

The highest temperature of the summer was recorded on January 26, when the mercury rose to 39.3degC in Ashburton.

"This was New Zealand’s 11th-equal hottest temperature on record," he said.

john.lewis@odt.co.nz

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