"The North Island will have patchy rain or drizzle developing in the west, especially from Waikato southwards," Marsters said. "It will be mainly fine in the east."
In the South Island, rain will become persistent and heavier in the west as the day goes on. In the east, scattered rain will develop in Otago and Southland, with cloud increasing further north.
Despite the showers, it will still be hot.
"Gisborne and Hastings will be the best spots in the country with temperatures reaching the high 20s. Sunday will be cloudier than Saturday in most places but it will be drier in the east and still be a fine day in most places."
Moving into Monday, the North Island will see patchy rain or drizzle developing in the west, especially from Waikato southwards. It will be mainly fine in the east.
In the South Island, rain will become persistent and heavier in the west. In the east, scattered rain will develop in Otago and Southland with cloud increasing further north.
Weather at a glance
Saturday:
Auckland - 22, sunny
Wellington - 21, partly cloudy
Tauranga - 25, sunny
Whangarei - 24, sunny
Taupo - 24, sunny
Christchurch - 23, partly cloudy
Dunedin - 20, cloudy
Sunday:
Auckland - 25, cloudy
Wellington - 20, rain
Tauranga - 26, cloudy
Whangarei - 27, cloudy
Taupo - 23, rain
Christchurch - 28, partly cloudy
Dunedin - 23, showers