As you may or may not already know, Australia is one of the few countries in the world that starts each season at the beginning of a month — marking December 1 as the start of summer, March 1 for autumn, June 1 for winter and September 1 for spring.
Other commenters pointed to the far more varied seasonal calendars that Aboriginal and Torres Strait Islander Peoples follow — who have developed an intricate understanding of the relationship between country and climate over tens of thousands of years.
"I grew up in the bush and the Indigenous people lived by and knew the local seasons."
"The Bureau of Meteorology actually have specific seasons based on traditional First Nations knowledge from different regions of Australia."
—u/SydneyRFC
This led me into a deep dive of this Indigenous Weather Knowledge calendar — which tracks the patterns and seasonal characteristics of 17 different First Nations Countries.
For instance, on D'harawal Country — which extends from the southern shores of Sydney Harbour, to the northern shores of the Shoalhaven River in NSW — the traditional landowners observe six different seasons.
By comparison, the Walabunnba calendar — which covers a region 300km from Alice Springs in the central desert of Australia — follows just two seasons.
In conclusion, Australia's sweeping, generalised seasonal calendar is totally wrong — and if you want a more accurate representation of the weather patterns in your area, you can find the closest First Nations calendar for your location here.
And let me know if you find it to be a more accurate summary of your hometown's seasonal patterns!