Severe northwest gales and heavy rains are expected today and tomorrow, with gusts up to 140km/h and 160mm rain predicted for Canterbury.

MetService has issued severe weather warnings, with Canterbury high country and plains, Southland and Otago affected by gales until midmorning tomorrow.

Marlborough, Wellington and Wairarapa were expected to be hit from this evening, continuing into tomorrow night.

Gusts up to 140km/h were expected for the Canterbury high country, with 120km/h in other areas.

Headwaters of lakes and rivers in Canterbury south of Arthur's Pass were also set for a drenching tonight, with up to 160mm of rain expected over 13 hours about the divide.

Heavy rain was also expected in Fiordland, Westland south of Otira, as well as headwaters of lakes and rivers in Otago for about 24 hours from 10am today.

MetService also warned of up to 8cm of snow near the tunnel on Milford Road, and up to 3cm near the summits on Lindis Pass and Crown Range Road.