Bands of rain will move northwards from the bottom of the South Island through the first part of the week, preceded by strong northwesterlies and followed by a strong, cold and wet southerly.
Heavy rain and strong wind watches are in place for various parts of the South Island, some starting tonight and extending through to Tuesday.
One heavy rain warning was in place for Fiordland and four heavy rain watches for Southland, Otago and Clutha, and Westland south of Ōtira.
There is also a heavy orange rain warning for Fiordland, and strong wind watches are in place for Southland tonight and North Otago and Canterbury for Monday.
MetService said 210 to 260 millimetres were likely to accumulate about the ranges, and 70 to 120 millimetres near the coast. It said peak rain rates could be up to 35 millimetres an hour in the ranges, and thunderstorms were possible.
MetService forecaster Aidan Pyselman said a front was set to move slowly over the lower South Island from the early hours of Monday.
“It’s preceded by strong northwesterlies, and then it’s going to bring some heavy rain as it moves up the South Island.
“The North Island is also set for a bout of rain as the front moves up the country Tuesday and Wednesday.
“Then … we’re also going to see some really strong southerlies in behind it as we move through the week, and also some much cooler temperatures as well. It comes up onto the North Island during Wednesday, Thursday.
“By about Friday we should see temperatures slightly rebounding and warming up again.”