A southerly change pushing over the upper South Island and North Island during Monday brings in a cooler patch of weather and some welcome rain. A ridge starts to move in fairly promptly behind this change.
For the upper North Island expect cloud to build in the morning with a shower or two possible, afternoon rain moves in possibly heavy with thunderstorms as winds change southwest. Rain clearing in the evening although a shower or two may linger till overnight. Temperatures reaching into the mid twenties before the southwest change moves in.
Fresh southerlies develop about the lower western North Island in the morning bringing rain or showers, clearing in the afternoon for the most part although showers about Palmerston North through to the Central North Island may not clear till evening. Southerlies freshen early in the morning about the Wairarapa bringing showers, hitting Gisborne early afternoon at which point rain is more likely with a chance of thunderstorms.
For Nelson and Marlborough, conditions are dry first thing then a few showers may develop during the morning, perhaps hanging around till evening although they will be quite isolated in nature so some may remain fairly dry especially about coastal Marlborough.
Early rain for Canterbury eases to the odd drizzle patch which clears by evening, cool southerlies swing around to the east or northeast in the afternoon. Any early showers clear Southland and Otago then breaking to sunny spells, southerlies tend northeast in the afternoon. The West Coast has a mainly sunny day, any early showers about Buller clear, light southeasterlies tend westerly in the afternoon.
Image – Monday 18th December 1pm MSLP / Rain map – weathermap.co.nz