Big dry, then floods in exceptional year

EXTREMES: Whanganui experienced extremes of wet and dry during 2015, including floods in June.PHOTO/SUPPLIED

Whanganui experienced the extremes of wet and dry during 2015, according to figures released recently by the National Institute of Water and Atmospheric Research.

Climate scientist Nava Fedaeff said Whanganui went from its second-driest January since 1890 - just 1.6mm of rain - to the worst floods ever recorded in the city, in June.

Summer and early autumn dry conditions continued through February and March, but in April that changed. April 2015 was one of the wettest months Whanganui has ever experienced - with 235mm - and May was nearly as wet.

Then on June 19-20 came the floods which saw the central business district inundated by water, dozens of people evacuated, and houses badly damaged. On these two days 140mm of rain fell in Whanganui.

"The Whanganui climate station at the airport recorded its highest-ever June one-day rainfall since 1937 on June 19, when 79mm over 24 hours was measured," Ms Fedaeff said.

She said Whanganui's rainfall total for 2015 was near normal - with 1070.4mm of rain.

The highest temperature recorded during 2015 was 29.8C on January 28.

The lowest was -0.8C on July 14.

Ms Fedaeff said throughout New Zealand as a whole, temperatures were within 0.5C of normal.

There were some notable exceptions, such as -21C recorded at Tara Hills on June 24, the fourth-lowest temperature ever observed in New Zealand.

As for rainfall, Ms Fedaeff said most regions had dry or normal conditions in 2015.