Sorry, its 330 mm or 13 inches just south of Moreton Bay.30 ml is just a shower. Where I work we got 210 in one day. But yes even a little rain in a fresh burn will have serious consequences. Happens to us every year.
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"Several major highways were cut off, while theme parks closed in southeastern Queensland after some of the heaviest rain in months fell in the state. Local media showed video footage of dozens of vehicles being swept away in flash flooding.
Standing water reached 330 millimeters (13 inches) in some areas and Australia's Bureau of Meteorology tweeted that over 100 millimeters of rain was expected to fall across the night and early Saturday morning in many other locations.
The Bureau of Meteorology for Queensland also told drivers to "take care on the roads — if it's flooded, forget it."
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https://www.dw.com/en/storm-flooding-misery-follow-bushfires-in-australia/a-52049688