A rain band travelling across large parts of the country is expected to reach Queensland in coming days, bringing rain and cooler temperatures to large swathes of the Sunshine State.

Weather experts predict the band, estimated to span an area roughly 3000km in length, could reach parts of Queensland as early as Wednesday.

“There’s a thick cloud band that’s approaching from north-western Australia, so it’ll move into the west or far west of the state on Wednesday ... south of Mount Isa,” senior meteorologist Shane Kennedy said.

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“That cloud band will steadily move east over the following few days, so Thursday (into) Friday.”

Tropical moisture flowing over Australia from the Indian Ocean has produced the large cloud band, according to the Bureau of Meteorology.

There are concerns the storms could cause flooding and road closures across the parts of the state.

“We could see some moderate rainfall, and if you see it over a short period (of time) there could be some potential for flash flooding, potentially some local creek and river rises,” Kennedy said.

The Capricornia area, particularly Rockhampton, will likely be the most impacted area, with up to 60mm of rainfall expected on Friday.

Temperatures across the state are also expected to fall, with Stanthorpe in the Southern Downs Region expected to reach a low of 5 degrees as early as Wednesday.

“Most places (in Queensland) will see about a 10C drop over the next couple of days,” Kennedy said.

There are fears the Brisbane marathon could be washed out as organisers prepare for Sunday’s event that will see 14,000 runners participate in the cross city run. Organisers said rain will not affect the race “unless conditions are deemed unsafe”. “It’s always a good idea to check the event’s official website or contact the organisers for any updates or changes due to weather conditions,” they said. Brisbane is expected to have its heaviest day of rain on Monday, reaching a possible 25mm.