A low pressure system east of New Zealand on Monday brings a cold southerly airflow for the South Island, milder westerlies further north.
For the western North Island expect mostly cloudy skies, the odd shower about also. The shower risk increases after midday and there may be the odd heavy fall in the evening. The east coast has a mainly dry day with increasing high cloud, there may be a spot of rain in the evening however. Overnight strong cold southerlies move into Wellington bringing rain.
Some morning rain or showers for the West Coast of the South Island then clearing with sunny areas developing from afternoon, showers may hang about Buller through till evening however. A sunny start about Nelson and Marlborough then showers move in during the afternoon, some could be heavy with thunderstorms and hail. Showers ease in the evening then more persistent widespread rain moves into Marlborough overnight with snow lowering to 400m.
Rain about South and Mid Canterbury spreads into North Canterbury during the morning with cold southerly winds, snow lowers to 500m during the afternoon then 300m overnight. Rain or showers from morning for Otago, Southland may have a dry start then showers push in from midday as cold southerlies freshen. Snow about the far south to around 400m, lowering to 200m in the evening then clearing overnight.
Image: Monday 24th September 2018 3:00pm MSLP / Rain map – weathermap.co.nz