A series of severe weather warnings and watches have been issued across the South Island, with strong northwesterly winds and heavy rain expected to impact the region today and tomorrow.

MetService has issued Heavy Rain Warnings for Westland and Fiordland, marking only the second time this year such alerts have been necessary for these regions. The downpours are expected to bring up to 200mm of rain in the Westland ranges and 100mm closer to the coast, leading to the risk of surface flooding, slips, and hazardous driving conditions.

MetService meteorologist Clare O’Connor said the rainfall will be significant.

“These areas are well below their usual year-to-date rainfall totals, and surface flooding, slips, and adverse driving conditions are worth looking out for,” she said.

A Heavy Rain Watch has also been issued for Southland, including Stewart Island, with periods of heavy rain expected from Monday afternoon.

Meanwhile, strong northwesterly winds ahead of the rainband are pushing temperatures as high as 30°C in parts of the South Island. This has led to Strong Wind Watches for the Canterbury High Country, Canterbury Plains, Otago, and Southland, with wind gusts of up to 100 km/h possible.

Wellington is also expected to feel the effects, with a Strong Wind Watch in place from early Tuesday as northwesterly winds arrive in the lower North Island.

O’Connor said the warm northwesterlies will be short-lived, with cool southerly winds quickly following the rainband, leading to a sharp temperature drop.

“This switch in wind flow brings a bit of a rollercoaster in the temperature charts. Cricket fans in Dunedin on Tuesday will need to layer up, with only 15°C expected.”

The change in conditions could also bring thunderstorms to the upper South Island and much of the North Island on Tuesday afternoon and evening, except for the eastern regions.