A frontal boundary is bringing rain to the South Island this morning. Heavy rain is likely with this system and due to the slow movement of the system, this could be a prolonged heavy rain event for the western and northwestern South Island.

Government forecaster MetService has issued Heavy Rain Warnings for:

• Westland, south Otira-  Between now and 9am Sunday, 300 to 500mm of rain is expected on the ranges. Rainfall rates of up to 20 to 30mm an hour are possible through this evening and again late Saturday night inot Sunday morning. Coastal sections may receive 150 to 200mm during this time.

• The headwaters of the Otago Lakes and Rivers- Through tonight, 150 to 200mm of rain is expected near the Divide

• Headwaters of the Canterbury Lakes and Rivers south of Rangitata River- Through late tonight, 150 to 200mm of rain is expected near the Divide. More heavy rain is possible Saturday and early Sunday

MetService has also issued a Severe Weather Watch for heavy rain for the northwestern South Island, including the Westland and Buller ranges north of Otira from tonight through early Sunday morning and western Nelson during Saturday and Sunday morning.

-WeatherWatch.co.nz