Road may be cut and towns isolated as parts of central Australia get “an entire year’s worth of rain” this week, bringing widespread floods.

Forecaster Weatherzone said the deluge could months of floods that could spread across parts of four states and territories.

“Some places in western Queensland could see six-12 months’ worth of rain this week,” it wrote on Monday.

“Longreach’s annual average is about 430 millimetres, and some models are hinting at accumulated weekly totals of around 400 millimetres in that region. The annual averages at Windorah (about 300 millimetres) and Charleville (about 490 millimetres) are also in the range of what some models are anticipating this week.”

Forecast models predict 100-300 millimetres of rain across a broad area of outback Queensland this week. Heavy falls are also expected to impact parts of the state’s east, as well as NSW, the Northern Territory and South Australia.

The warning came as a rescue operation began in SA’s far north on Monday to free three adults and a six-year-old child stranded in floodwaters.

The group was last seen travelling from Oodnadatta to Finke, about 300 kilometres away, last Friday.

They made contact with authorities on Sunday. Food supplies and a satellite phone were dropped, but the group remained trapped by floodwaters.

SA Police said later on Monday that all four had been retrieved and transported to Coober Pedy.

It follows flooding in northern South Australia, far-western Queensland and the south of the NT last week that cut roads and isolated some communities.

The Bureau of Meteorology issued a severe thunderstorm warning for Queensland’s north-western inland regions on Monday.

“Severe thunderstorms are likely to produce heavy rainfall that may lead to flash flooding in the warning area over the next several hours. Locations which may be affected include Camooweal, Selwyn and Mckinlay,” it wrote.

Weatherzone said a standout feature of this week’s system would be its slow movement, which will mean days of heavy rain in affected areas.

It said computer models disagreed on where and how much rain would fall.

“However, there is good model agreement that this week’s deluge will be intense enough to cause widespread flooding,” it said.

The downpour’s long-term impacts will be strongest in the Channel Country, which largely encompasses outback Queensland. The rain is also expected to fill Kati Thanda-Lake Eyre in coming weeks.