The MetService has issued an Orange heavy rain warning for the headwaters of Lake Wānaka and Lake Hāwea from 3am-12pm Thursday August 28.

An active front moving over the South Island on Thursday is expected to bring heavy rain and strong north to northeast winds.

Expect 100 to 120 mm of rain near the main divide and 60 to 80 mm within 20km east of the divide. Peak rates of 15 to 25 mm/h expected about the divide.

Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.

Anyone heading into Mt Aspiring National Park is advised to take extra care or delay travel.