Vintage dressing for transitional weather

I don't know if I'm alone in this, but I find it much easier to wear vintage when it's slightly cooler out than in the heat of summer. Vintage sundresses are comfortable and lovely, but they're not that practical on a bike (the longer skirts get caught up in my wheels and get all gunked up), and I don't really want to get a nice vintage piece all soaked in sweat.
The weather here in Chicago has been doing its thing lately, going from hot to pouring rain to downright chilly, all in the course of a single day. It's hard to dress for that, but there are a few things that help.

1. Layering.
Layers. I know, revolutionary, right? But seriously, a cardigan and a scarf or a lightweight trench coat can make the difference between being miserable and shivering when the weather takes a turn for the cooler, and being comfortable. I am, frankly, nuts about cardigans.
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This isn't even all of them. My favorite are my vintage cashmere cardigans, which are super soft and versatile, but JCrew is one of my go-to stores for classic cardigans, and I also really like Forever21 for fun, printed styles.

2. Long sleeved tops with shorts.
I know it probably sounds counterintuitive, but when it's really hot out, I almost always wear long or 3/4 length sleeves. It's actually a little cooler than letting the sun beat down on your bare skin (which isn't very good for you anyway), but it's also warmer if the clouds start to roll in.
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It's kind of hard to see my shorts here, but combination of a Breton striped top and high-waisted, printed shorts has a fun, French, pinup kind of feel, and looks great on a lot of different body types.

3. An elastic waistband is your friend.
It can be hard to find authentic vintage pieces with elastic waists, but they're worth keeping an eye out for. You'll see it on some pieces from the 60s and later, and they're fairly common on patio dresses and skirts (you'll sometimes see them labeled as "squaw" dresses) and items meant for square dancing. Wearing a very tight waistband in the heat of summer can be really uncomfortable, especially when sweat starts to collect in it, so something with a bit more give and flexibility can be a lifesaver. I don't always love the look of an elastic waist, so weather permitting I might belt it.
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The elastic panels on this 60s sundress make it one of the most comfortable pieces that I own.
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I adore the embroidery on this 70s era dress. It also has an elastic waist, although as you can see here, I belted it for a slightly more polished look.

During the cooler months I shoot for a classic, ladylike kind of look, but this summer I'm looking forward to playing around a bit with some pinup style looks. I've spent some time browsing through rompers and playsuits, something I never really thought I'd get into.
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I really love this adorable two piece playsuit from VintageRagsAndDigs. The size and fabric are customizable, and I believe it's made using a vintage pattern.

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Isn't this 80s does 40s romper to die for? It's on sale from TaraMiSioux on Etsy. I love the classic color and shape, and it looks like it would be really comfortable for biking.