Mr Glassey said looking forward to the week ahead, a front would spread north over the country through Monday and Tuesday.
"On Monday we're expecting rain to spread on to the South Island and the lower North Island with heavy falls in the west of the South Island.
"Then the rain should spread over the rest of the country on Tuesday."
A brief southerly change would come in behind the front, which would drop temperatures back down.
The front would clear the country on Wednesday, and more fine weather was forecast for the end of the week, Mr Glassey said.
"It's looking mainly fine... for the second half of the week.
"But with the ridge of high pressure coming on it'll bring some fine weather but the mornings could still be quite frosty in some areas."
Tomorrow's forecast
Whangarei: Mainly fine. Northerlies. High 17C Low 11C
Auckland: Mainly fine. Northerlies. High 16C Low 11C
Tauranga: Cloudy periods, chance shower. Northerlies developing. High 15C Low 10C
Hamilton: Mainly fine, cloud increases evening. Northerly breeze. High 16C Low 7C
Wellington: Occasional rain develops morning. Northerly strengthens. High 13C Low 10C
Christchurch: Becoming cloudy, few spots rain. Northeasterly. Late showers with southwesterlies. High 15C Low 4C
(Source: MetService)