The MetService has issued an Orange heavy rain warning for the headwaters of Lake Wānaka and Lake Hāwea.

A front will move onto Fiordland today (Wednesday October 23) bringing heavy rain, then move slowly northwards tomorrow.

Expect 175 to 250 mm of rain near the divide and more than 100 mm within 20 km east of the divide. Heaviest falls are likely during Thursday morning when intensities of 15 to 25 mm per hour are possible.

The effects may be amplified by snow-melt and there is a moderate chance of upgrading to a Red warning.

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

The warning is effective from 4pm today through to 4pm Thursday October 24.