For our area, I think the issue wasn't so much average temperature for September (we were only a bit below) but the fact there was so little sun and so many rain days - always makes it 'feel' cold.
Also, we haven't had a 20 C day yet; not even close and most years we would have by now. That break in the cold hasn't really happened - although it should finally make it today with a bit of luck
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In terms of rainfall, this is our second wettest year to this date during my 20 years of records, beaten only by 2011. All the more remarkable for having such a dry start (2011 'cheated' by having almost 400 mm in Jan/Feb!) Certainly our wettest winter/early spring.
PS: I think the most striking feature of the last few months will be surface water/ run-off (except for the south central/ south-east dry spot). For example, the Grampians storages have just passed the 75th percentile for inflows, despite a terribly hot & dry start to the year
http://www.gwmwater.org.au/cumulative-inflows. Expect MDBA figures for northern Vic for winter/spring will be similarly exceptional.