A severe weather warning is out for Buller, Westland and the Canterbury Headwaters where between 50mm to 100mm of rain could fall over Sunday.
Tomorrow heavy rain should turn to showers that will affect most of the country, Griffin said.
Temperatures will plunge as the wind whips around to a more southerly direction. South Islanders would gets lows in the single digits and highs in the low teens, Griffin said.
"The North Island will have showers, possibly heavy falls gradually easing into the evening. The South Island is going to see rain developing on most of the east coast into the evening."
Scattered showers would pepper the country on Tuesday and further into the week, Griffin said.
"It looks like typical springtime weather. Closer to the end of the week it looks like it will still be a bit rainy."