Auckland has recorded its warmest January in 70 years, with residents sweltering in unrelenting humid weather.
Warm, humid tropical air flows caused record mean January temperatures in four centres, the National Institute of Water and Atmospheric Research says.
Auckland recorded a mean air temperature of 20.5degC, its highest since 1945.
Motueka recorded its highest mean temperature since 1956 of 19.4degC, Kaikohe recorded 21.2degC, its highest since 1973, and Kerikeri recorded 20.9degC, its highest since 1981.
The highest temperature recorded nationwide last month was in Gisborne on January 24, with 34.4degC.
NIWA says high pressure anomalies to the east of the country caused a northeast flow to deliver tropical air flows.