MetService is forecasting a period of heavy rain which may reach warning levels in Fiordland and the far south of Westland.
A front is forecast to cross the area tomorrow.
Up to 80mm could fall in Fiordland between 4am and 8pm, and in Mt Aspiring National Park between 10am tomorrow and 2am on Friday.
A MetService spokesman cautioned trampers and other people heading into these regions, especially about higher areas.
Meanwhile, rain and snow is forecast near the Milford Road tunnel (State Highway 94) tomorrow.
The Milford Road Alliance advised there may be delays for road users if snow had to be cleared.
Showers were expected on Friday, before a fine but cloudy weekend.
