Up to 150 millimetres of rain is expected to fall across parts of the South Island

MetService has issued heavy rain warnings for the Tasman ranges - north-west of Motueka, Buller, the Westland ranges and parts of Canterbury, for this afternoon.

Strong wind warnings are also in place for Wellington, Marlborough and the Canterbury High Country.

Meteorologist Devlin Lynden says people in these areas could be starting to feel the weather now but the worst will come later this afternoon and overnight.

There's also a heavy rain warning for the Tararua Range from 6am tomorrow.