An Orange alert has been issued today for Fiordland, Southland and Stewart Island by Emergency Management Southland (EMS).

It is expected there will be periods of heavy rain in Fiordland, up to a total of 200-250mm, between 11am Thursday (4 Aug) and 6pm (6 Aug).

The heaviest rain is expected during Friday afternoon, evening and overnight Friday when rainfall rates may reach 15 to 25 mm/h and thunderstorms are possible.

There is also a Strong Wind Warning (Orange alert) for Southland, Fiordland, Stewart Island, lasting from 6am till 11pm Friday (5 Aug).

EMS advises strong wind gusts could damage trees, powerlines and unsecured structures. They advise driving may be hazardous, especially for high-sided vehicles and motorcycles.

Northwest gales are forecast to be severe at times, with gusts reaching 140 km/h in exposed places.