In Otago and Southland, a mostly sunny morning will give way to a cloudy afternoon.
The West Coast will be hit by showers and then heavy rain from the late afternoon, WeatherWatch said.
The MetService has a heavy rain watch in place on Monday evening for Westland and the ranges of Nelson and northern Marlborough.
As of 5.30am today, Alexandra was the coldest town in the country with a temperature of -2.9 degrees Celsius, according to MetService.
Kaitaia was the warmest with 12.2C and New Plymouth the wettest, having had 3.2mm of rain.
That pattern of morning showers is expected to repeat over the next few days, MetService says.
Wellington is heading for a windy top of 13C today as the northerly winds turn to gales in the evening.
A high of 11C is expected for Christchurch as cloud increases in the afternoon before rain hits overnight.
Main centre forecast
Whangārei
Cloudy periods. A few showers this morning and evening. Westerlies turning northerly and strengthening afternoon. High 17C, low 11C
Auckland
A few morning showers, then fine. Cloud increasing evening. Westerlies turning northerly afternoon then strengthening. 16C, 11C
Hamilton
Cloudy periods. A few morning showers. Westerlies turning northerly afternoon. 15C, 9C
Tauranga
A few early showers, then fine. Showers returning this evening. Westerlies turning northerly afternoon. 16C, 11C
Wellington
Mainly fine. Chance shower from afternoon. Northerlies rising to gale evening. 13C, 10C
Nelson
Fine at first. A few showers developing this afternoon, turning to rain late evening. Northerlies becoming strong late evening. 12C, 6C
Christchurch
Fine. Cloud increasing evening, then rain overnight. Northeasterlies becoming strong this evening. 11C, 2C
Dunedin
Cloud clearing to fine early this morning. Periods of rain developing late afternoon. Northeast breezes. 10C, 4C