The MetService has issued an Orange heavy rain warning for the headwaters of Lake Wānaka and Lake Hāwea from 1am-5pm Tuesday July 29.

A front moving east across the country is expected to bring heavy rain and strong north to northeast winds.

Expect 130 to 180 mm of rain near the main divide and 80 to 100 mm within 15km east of the divide. Peak rates of 10 to 20 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.