The North Island would continue its fine spell through Wednesday before the front made its way north on Thursday. Rain was forecast for most places later in the week.
Loots said at this stage the heaviest rain mid-week would affect the "usual suspects", along the South Island's West Coast.
But when the low pressure system arrived Thursday it could bring heavy rain to parts of the South Island's east coast, central parts of the country, and the North Island into Friday.
- Additional reporting Otago Daily Times
Today's weather
Mainly fine, apart from morning cloud. Chance afternoon shower. Light winds and afternoon sea breezes. 19C high, 9C overnight.
Mostly sunny, with isolated afternoon showers. Light winds and afternoon sea breezes. 19C high, 10C overnight.
Mainly fine, but chance afternoon shower. Light winds. 19C high, 6C overnight.
Cloudy periods, a few evening showers. Light winds and sea breezes. 18C high, 10C overnight.
New Plymouth Fine apart from chance afternoon shower. Southeast breezes tending southwest. 17C high, 6C overnight.
Napier Some morning cloud, then fine. Light winds and sea breezes. 16C high, 5C overnight.
Whanganui A fine day. Westerly breezes. 19C high, 7C overnight.
Wellington Fine apart from some morning cloud. Northerlies becoming fresh afternoon, changing southerly overnight. 15C high, 8C overnight.
Nelson Fine. Light winds and sea breezes, southwesterlies developing evening. 16C high, 6C overnight.
Christchurch Morning cloud, then sunny spells. Light winds. 17C high, 4C overnight.
Dunedin Morning cloud and possible drizzle, then fine. Light winds. 13C high, 8C overnight.