Enjoy the spring-like weather while it lasts - there is a cold snap on the way, forecasters say.
"The week starts off warm and gets progressively colder," WeatherWatch.co.nz head weather analyst Philip Duncan said.
Today would be the warmest day of the week, with a maximum temperature of 18C, and northerly winds. The balmy high was evidence of the beginning of spring.
"The spring pattern is here. To me, spring is absolutely here now. It was here a couple of weeks ago."
The meteorological date for the start of spring is September 1. Days are getting longer, with the sun now setting about 5.45pm. After the equinox on September 23, days would become longer than nights.
Mr Duncan said the region could expect plenty more westerly weather cycles if the El Nino weather phenomenon began to take hold this year, as predicted.
El Nino is a climate pattern associated with unusually warm ocean waters in parts of the Pacific Ocean. It is characterised by westerly winds, which could lead to a dearth of rain in eastern areas such as Hawke's Bay.
Cloud is expected to increase later today. Tomorrow a front would bring rain about the ranges, and scattered showers elsewhere, with winds turning northwest.
"There'll be some spits of rain, but not a huge amount."
A southerly change would occur on Wednesday, causing the daytime high to drop to 14C. Although it would be "mostly fine" for the rest of the week, temperatures would continue to fall.
MetService meteorologist Claire Flynn said there was also a chance of showers on Wednesday and Thursday.