Emergency services were called to a creek at Boompa on Queensland's Fraser Coast shortly after 11am on Monday after reports a man had been found unresponsive.
The man was declared dead after being found in Smothering Creek on Boompa Road, Queensland Police said.
An investigation into his death has begun, with police to prepare a report for the coroner.
Further south, six campers were rescued after becoming stranded by floodwaters at a public campground in Leyburn in Queensland's Southern Downs.
Queensland Fire and Rescue Swiftwater crews responded to the call for help at 7:45am on Monday.
They rescued three men aged 71, 47 and 26 and two women aged 68 and 26 without incident around 11.15am.
There were no reports of physical injuries, Queensland Police said in a statement.
Torrential downpours across Queensland between Thursday and Monday left many rivers and roads flooded across the state's south and east.
There are warnings of more rain and flooding to come.
Flash flooding hit Laidley Creek and Glenore Grove in the Lockyer Valley, west of Brisbane, closing some roads, Queensland Police warned on Monday.
The highest recorded four-day totals were spread across the state, with Blackdown Tableland, near Rockhampton, recording 439.4mm to early Monday.
Lower Springbrook, near the Gold Coast, recorded 325.2mm, while Nambour, near the Sunshine Coast, copped 314.2mm.
Brooweena, inland of K'gari, received 299.6mm.
Meteorologist Angus Hines said the system behind the downpours was unusual.
''The widespread rain bands with heaps of cloud cover, much cooler temperatures, and then the storms in that situation are really driven by what's going on in the higher parts of the atmosphere,'' he said.
On Sunday evening, thunderstorms were briefly connected from southern Queensland to Bass Strait, as a swift-moving system passed towards Australia's east coast.
The storm band raced over most states, propelled by strong winds in the upper atmosphere.
"But that steering wind sort of just tapered off through the night last night over (Queensland's) Darling Downs," Mr Hines said.
Flood warnings are current for Warrill Creek and the Bremer River in the Lockyer Valley, the Macintyre and Moonie rivers in the south, and the Mary River near the Sunshine Coast.
Western Queensland also remains on alert, with warnings current for the Warrego River at Charleville, the Bulloo River in Quilpie, and the Barcoo River at Blackall.
The Bureau of Meteorology said Queensland's weather was set to return to more typical spring conditions as the week continued.
Hot and humid days are expected to give way to more subdued afternoon showers and storms.
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