In all of New Zealand the highest summer temperature was 34.7C, recorded at Lake Karapiro on January 4.
Whanganui's average temperatures were more than 1.2degC warmer than usual, and that average was driven up by noticeably warm nights. On the hottest day, February 10, the overnight temperature was 20C.
A marine heatwave that began in November persisted through the summer and was especially strong in seas to the northeast of the North Island, Niwa said.
The La Niña weather pattern brought more easterly winds than usual, and many were warm and humid.
The result was long fine periods, interspersed with heavy dumps of rain.
The first dump happened in December. Between December 12 and 14 Whanganui Airport got 75mm of rain. On December 15 the temperature reached a December record of 29.3C.
Another 48mm of rain fell on December 28, the second wettest December day recorded there. It brought the December rainfall total to 182mm, and made that month the third wettest December on record.
in January, by contrast, virtually no rain fell at the airport. The total was a mere 0.2mm for the month. It was the driest January on record for Whanganui.
Then, in February, the city got 113mm across Waitangi Weekend, February 5-6, with 82mmm on the first day. Another 76mm fell across the next weekend, February 11-13.
The second dumping came with Cyclone Dovi, the only cyclone to make landfall in New Zealand for nearly four years, Niwa said. It brought Whanganui's third highest wind gust since 1977 - 106km/h at Whanganui Airport.
The rain and wind made for power outages across the region, and the Mangaiti Stream washed out Kauarapaoa Rd yet again.
All of this made February the second wettest Whanganui February on record.
The overall result has been that we got 150 per cent of the usual summer rain, and solid moisture levels are above average as we go into March.
RECORDS FOR WHANGANUI AIRPORT WEATHER STATION
December 15 - 29.3C second hottest December temperature
December 28 - second wettest December day
Third wettest December month
January - driest month on record
February 5 - 82.6mm of rain - wettest February day
February 10 - 32.7C warmest recorded temperature
Second wettest February month