I ride all year round in Brissie. I find my comfort level depends on when I ride, distance, speed and my bike setup.
First, I ride to and from work in the morning and arvo when it’s cooler, not in the middle of the day.
I ride 6km each direction which is manageable. In winter I barely break a sweat. In summer I have a shower on each side. I can and sometimes do get away without showering by riding slowly. Or I just catch PT if I’m going somewhere else after work.
The other thing I noticed is that not wearing a bag helps a lot with reducing sweat on my back. I have a basket on the back of my bike and just throw my bag in. A lot of other people use pannier bags.