All up, that tally reached 1052 millimetres, according to the Bureau of Meteorology. (By Tuesday morning, that tally had grown by another 37 millimetres, while the nearby air weapons range copped another 176 millimetres.) Loading Replay Replay video Play video Play video The total beat the previously weekly high from January 1998 of 886 millimetres although that event included the "night of Noah' when a record daily tally of 548.8 millimetres fell. It's a wet part of Australia, we know, but the past week has delivered almost Townsville's entire annual average of 1157.9 millimetres at a site where the data goes back to 1940. In other words, a year's rain in a week for the town.

"This event is just an unprecedented monsoonal burst," says Grace Legge, a senior meteorologist in the bureau's extreme weather desk, adding that many stations are likely to set multiple-day records. To Townville's west, the aptly named Upper Bluewater site clocked up 2068 millimetres in the week to Monday morning, according to Weatherzone. Queensland Fire and Emergency Services crews responding to flood conditions in Townsville. Credit:AAP How extensive is the flooding? With so much rain, dams in the region are not surprisingly overflowing. The bureau has issued warnings for many Queensland rivers.

Reports on Monday morning had some 500 homes in Townsville flooded with more expected to follow, and more than 1100 people rescued from their home. The Ross River Dam, which covers a 750 square-kilometre catchment area near Townsville, opened its gates fully on Sunday evening local time. That meant the release of 2000 cubic metres - or 2 million litres - per second into the river. Even so, the dam's capacity peaked near midnight, local time, at just shy of 250 per cent full. Helpfully, the dam has an automated Twitter feed, including this posting, show the dam had dropped 5385 million litres - or about 2.2 percentage points - in the previous hour:

It wasn't that many months ago that Townsville and much of north Queensland was enduring one of its driest winters on record. For most of the two years between 2016 and 2018, the Ross River Dam was between 15 and 25 per cent full. Such a flip "often happens" in that part of Australia, where regions can grow "from well into drought to receiving huge amounts of water", Ms Legge said. What's causing all the rain? The onset of Australia's annual northern monsoon didn't officially arrive until January 23 – just two days shy of the latest recorded, on January 25, 1973.

The bureau's trigger location, though, is Darwin, and other parts of the north had already been experiencing monsoonal rain – not least the Cairns region, which reported record floods. Daintree Village, for instance, collected 405 millimetres on January 27 alone. The driver of the big rain event is a deep low near Mount Isa, south of the Gulf of Carpentaria. "It's just sat there," says Jonathan Nott, a professor of geoscience at the Cairns campus of James Cook University. "It's drawing air in from the Coral Sea." That moist air – from the equator – is converging with south-easterly winds around the Townsville region. "It's just producing an abundant amount of rains," Professor Nott says. The monsoonal trough that has extended across the region has been "very stationary", meaning the heavy rainfall has "pretty much been going on for nine days", Ms Legge says.

What's the outlook? Predicting just how fast the trough will edge southwards and/or weaken is difficult. For now, the forecast is again for 100 millimetres or more for the region on Monday alone, including from near Ingham in the north, through Townsville, down to Bowen. The rainfall centre is predicted to shift towards Mackay on Tuesday but that will still leave falls of 50-100 millimetres for the Townsville area. Even then a couple more days of 50 millimetres will likely follow, the bureau predicts.

"From Bowen up, everything is pretty much saturated," Professor Nott says. Ms Legge agrees: "We've got multiple days of it to come." With the catchments so wet, further rain is likely to add to run-off immediately. Townsville residents on Friday. Credit:AAP What effect is climate change having?

The Bureau of Meteorology and CSIRO's latest State of the Climate report notes "northern Australia has been wetter across all seasons", particularly in the north-west. Much of the Cape York region is also among the places getting wetter. With global warming, the atmosphere can hold about 7 per cent more rain for each degree it heats up. The world has warmed more than a degree since pre-industrial times, including the moisture available for big rain events. Professor Nott says peer-reviewed research is showing that in north-east Queensland, rainfall events are dumping more rain, particularly in storms. "We certainly know rainfall variability is increasing," he says, adding that means more periods of big highs and big dries for rivers. Even though there have been big falls in inland Queensland, they are too far north to have an impact on the Murray-Darling basin. Instead, some of the run-off will eventually make it to Lake Eyre, Professor Nott said.

One possible plus from the extended wet spell over northern coastal Queensland is that the risk of another coral bleaching event may have receded. The rainfall and cloudiness will cool sea-surface temperatures that had been pointing to a third big bleaching event in just four years for parts of the Great Barrier Reef. Still, all that sediment flowing down the rivers won't be great for corals or sea-grass beds that provide food for myriad fish and dugongs. The problem may be exacerbated to the extent that fertilisers and pesticides end up flowing out over the reach along with the clay, Professor Nott says. "It's an ecosystem under stress," he says. The floods "just make it that much more difficult".