My current commute is about 6km, with a few hills. In the middle of winter the temperature at 6.45am can get down to 3˚C (37˚F), whilst in the middle of a bad summer the temp at 6.45am could be as high as 30˚C, (86˚F) with high humidity.
I would love to be able to wear work clothes, but as someone who sweats at the drop of a hat, I wear a lycra cycling jersey and cycling shorts throughout the year. I hang them up at work and have a wash and get changed into clean clothes that I store at work. At the end of the day the cycling gear is dry and fresh enough for me to ride home. Often I will dump the backpack when I get home and do another 20 to 30km for funsies.
All my jersies are treated with anti-stink, so I get 2-3-4 (! in winter) wears out of them before washing. Fresh shorts every day.
I do this even though the before- and after-ride cleaning and dressing takes as long as the commute to work itself. Doesn't phase me. This is the most convenient way for me to do things. I remain sane because I get to ride every day, and I feel fresh at work.
And I get to annoy the type of people who want to judge me for wearing lycra on a 6km commute
.