Heavy rain and strong winds are on their way to the South Island, according to MetService.

Heavy rain is expected to hit Westland south of Otira and Fiordland on Tuesday morning - with between 100mm-150mm expected to fall.

The headwaters of the Otago and Canterbury lakes and rivers can expect the same amount of rain, which could see around 25mm fall in an hour.

Meanwhile, a strong wind warning is in place for the Canterbury High Country. Severe gales around 120km/h are expected to hit mostly exposed areas from early Tuesday morning.

The MetService is warning that strong wind gusts could damage trees, powerlines and unsecured structures and that riving may be hazardous, especially for high- sided vehicles and motorcycles.