Why seasons of Australia are reversed as compared to that in the northern hemisphere?

Australia's seasons are not reversed compared to the Northern Hemisphere. Both the Northern and Southern Hemispheres experience summer, autumn, winter, and spring at different times of the year.

In the Northern Hemisphere, summer occurs from June to August, autumn from September to November, winter from December to February, and spring from March to May. In the Southern Hemisphere, summer occurs from December to February, autumn from March to May, winter from June to August, and spring from September to November.

So while the seasons in Australia and the Northern Hemisphere do not occur at the same time of the year, they are not reversed.