A Department of Conservation (Doc) team began working on a new section of track in the valley, between Sandy Bluff and Bedford Bridge, last winter.
The 4.4km section is about two hours’ walk from the Paradise road end, in the Mt Aspiring National Park.
Doc Queenstown senior ranger Susie Geh said a week of rock-blasting and another week of track-clearing was needed to complete the new track.
"The poor summer we’re having, and current weather bomb, mean we can’t provide an exact date for reopening as the terrain makes track construction difficult to continue in adverse weather conditions."
Parts of the track were washed away by river erosion caused by a massive landslip in the Dart Valley in January 2014, and the erosion also claimed a temporary bypass track a year later.
The slip also caused a 3km-long lake to form further up the valley.
The Rees-Dart track is a four-to-five day circuit, usually accessed from near Glenorchy.
