Munga-Thirri-Simpson Desert National Park - the nation's largest national park - is again welcoming visitors after its annual summer closure.

The park, which spans 3.6 million hectares in the state's Far North, offers visitors unique four-wheeled-drive experiences and unrivalled views of the Milky Way enjoyed while camping under the night skies.

Nilpena Ediacara National Park, in the Flinders Ranges, has also re-opened for visitors keen to discover its ancient past through guided tours that provide an insight into its significance as an Ediacaran fossil site.

The Fossil Field Exploration Tour takes guests into the heart of ongoing research within the fossil fields, where scientists have found the oldest evidence of complex life on Earth.

The Simpson Desert is made up of 1100 parallel sand dunes, some of which are 200km long. Vehicle tracks such as the Old Andado, Colson or Hay River tracks have been made in the dips of the dunes and run for tens of kilometres.

Those crossing the Simpson Desert will pass through Witjira National Park, a popular destination for the national heritage-listed Dalhousie Springs, where visitors can swim in its pristine warm waters.

Public access routes, which provide vehicle access to locations including other desert parks, have re-opened, including Warburton Crossing, Level Post Bay, Halligan Bay Point, Walkers Crossing and Googs Track. Warraweena and Nuccaleena Mine routes remain closed due to safety issues.

National Park and Wildlife Service District Ranger Travis Gotch said cooler daytime temperatures made autumn and winter the perfect time to visit the state's desert parks.

"The best camping spots in Munga-Thirri–Simpson Desert National Park are in the central region where the gidgee woodlands provide shade, shelter and soft ground for pitching a tent," Mr Gotch said.

"The park is full of interesting wildlife, including the thorny devil, fat-tailed dunnart and wedge-tailed eagle."

He reminded travellers to stay safe by "ensuring vehicles are well-maintained and equipped, take extra water and food, use a HF radio or satellite phone, and tell a responsible person where you are going and when you expect to arrive".

A Desert Parks Pass (external site) is required to enter Munga-Thirri–Simpson Desert and Witjira national parks, which includes vehicle entry and camping, as well as important safety information and maps.

For current advice on desert park conditions, visit parks.sa.gov.au/know-before-you-go/desert-parks-bulletin (external site).

For up-to-date public road information outside of national parks, visit dit.sa.gov.au/OutbackRoads (external site).

To explore national parks or purchase a desert parks pass, visit parks.sa.gov.au (external site).

Entry to Nilpena is by guided tour only. To book, visit parks.sa.gov.au/parks/nilpena-ediacara-national-park (external site).