I am in the Northern hemisphere(transitioning from late-winter to spring) and I was just thinking about this topic today. For me, when it starts getting warmer, it's "shoe season"
. I can finally wear the cute heels and peep toe styles that I would have looked dumb wearing before with my toes becoming frost bitten! That is the most exciting thing for me. There are so many shoes I've been waiting for months to wear. Winter shoes just aren't as much fun to me.
It's isn't hot here yet so I wear pretty much the same outfits as I did before. I just bring a leather jacket instead of winter coat, and no hat or gloves or other winter accessories. Maybe a non-functional (like not meant to keep you warm) scarf but that's it. At this time of year I will still not wear bare legs, only tights or leggings with dresses and skirts.
Also, it is the perfect time of year for wearing all your blazers!
I love little jackets but it's usually too hot for them in summer (or the fabrics are meant for winter) and then when it's very cold and you have to wear a coat, I feel sooooo uncomfortable and restricted putting a winter coat on over a blazer, but I don't want to carry the blazer . . . so I take advantage and wear them at transition times.
Also, if I wear sweaters, they are lighter, like cotton or silk, etc. instead of merino or cashmere.
I think you just have to be prepared for getting to hot or too cold. Don't expect anything! If the forecast says sunny and 75 (fahrenheit) and you leave the house in sandals and sundress, chances are it will be 50 and raining. I keep umbrellas in my car and a mini one in my bag. Even if it's supposed to be warm I'll put something thin but long-sleeved in my bag too just incase. Sometimes the wind makes it cold too.
I think in general, with me and other women I notice, we tend to celebrate when it gets warmer by dressing up and putting more effort into the outfit, just because you can. You don't have to protect yourself from freezing and trudge through sloppy streets.