Record rainfall: September Whanganui's wettest on record - Niwa

September 2021 was Whanganui's wettest September on record, with 178mm of rainfall - almost half of which fell in a single day. Photo / Bevan Conley

Last month was Whanganui's second-wettest September on record.

The National Institute of Water and Atmospheric Research (Niwa) released its latest monthly outlook this week, looking at weather extremes across the country in September.

The report found that a total of 178 millimetres of rain fell in Whanganui over the month - more than double the typical rainfall for September.

That makes the month the second wettest September in the city since records began in 1890.

Close to half of the total rainfall fell within a single 24-hour period on September 13.

That day broke the record as the wettest single day in September since records began in 1937, with a total of 73mm of rain within Whanganui city.

That rain resulted in pockets of flooding and multiple slips across Whanganui and Rangitīkei, including in Turakina and the Whanganui suburb of Pūtiki, where some were evacuated due to rising floodwaters.

As well as the heavy rainfall, Whanganui city also recorded its fourth-coldest September day since records began in 1937, with a temperature of -0.2c on September 1.

Nearby, the Taranaki region is currently leading the stakes for the region with the most sunshine hours - sitting at 1884.

That is ahead of typical sunshine frontrunners Hawke's Bay, Marlborough and the wider Nelson region, which trail first, second and third respectively.

Nationwide, the report said a number of westerly flows over the month resulted in a higher number of strong frontal systems passing over the country.

The trend of higher-than-usual rainfall was also seen across most of the country throughout the month.