But scientists say climate change has pushed up land and sea temperatures and led to more extremely hot days and severe fire seasons.
Even after the release, as of Monday morning, the dam was still at 229 percent capacity, holding about 532,000 gigaliters of water, or roughly as much as Sydney Harbour.
Emergency services have been receiving incessant disaster and rescue calls made overnight from around the city of Townsville where evacuation centres have been filled up.
He said: "The modelling says what it is going to say - it could move up to 10,000, 20,000 (homes)".
"We have not been in this situation before", Queensland Premier Annastacia Palaszczuk is quoted as saying by the Australian Broadcasting Corporation (ABC).
According to CNN affiliate 9 News, supermarket shelves across the region are almost empty, with chains struggling to restock after Townsville Airport was closed and many major roads cut.
Deputy Commissioner Bob Gee urged residents to register their safety so family and friends knew they were safe.
The weather was atrocious overnight, with two police engaged in evacuation work rescued themselves after fast rising flood waters trapped them and washed away their patrol vehicle. "We still have many roads that are cut around those areas".
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"In Queensland, of course, we're used to seeing natural disasters, but Townsville has never seen the likes of this".
Townsville remains the hardest-hit area although floodwaters are affecting communities as far west as Mt Isa, in the state's interior.
The rain and flash flooding began a week ago, causing power and phone outages, closing roads and businesses and inundating homes. AAP Image/Andrew Rankin/via REUTERS Residents evacuating to higher ground in Hermit Park, Townsville, Queensland, Australia February 3, 2019.
Food and other supplies are on their way to flood-stricken Townsville as victims contemplate what they've lost and the long, messy clean up ahead.
Townsville Mayor Jenny Hill praised the plucky spirit of locals and urged the 185,000-strong community to "hang tough".
The Bureau of Meteorology said a slow-moving monsoonal trough was sitting above northern Queensland state, with some areas expected to receive more than a year's worth of rain before conditions ease.
Authorities have said more heavy rain is expected in coming days, with up to 20,000 homes at risk. "Unprecedented areas of flooding will occur in Townsville", a statement said, adding that there was a "risk to life and property".
Sasha Ngamoki posted photos on social media to pass on her gratitude to Chris from Armesto's Transport and BM Webb who pulled her family out of a unsafe situation.