What tips are there for dressing in a way that looks put together when getting around a city on hot, humid days? I often feel like a disheveled, sweaty mess by noon during the summer, while others seem to glide by in a cloud of composed coolness. How do they do it? — Adrienne, Paris

The unpredictable weather patterns and rising temperatures that are now part of our lives are changing how we dress in more ways than one, redefining the meaning of “hot girl — or guy — summer.”

No longer can anyone put winter clothing away in summer and vice versa, and a whole cottage industry of material scientists are putting their minds and pin cushions to creating fabrics to help people stay cool in the heat. Think, for example, of AIRism from Uniqlo and Polartec Delta and NanoStitch Air.

Yet most of these advances are geared more toward performance than daily life. For that, said Marie-Hélène de Taillac, the cult French jeweler who spends half of her year in Rajasthan, India, working with the artisans of the Gem Palace jewelry emporium, the place to start is with clothes in natural fabrics like cotton, bamboo and linen, because they “breathe” — i.e., let air flow between your skin and the outside environment.

Then, she said, it’s time to explode the biggest myth of hot month dressing — that less is more.

“The worst thing you can do is wear tiny clothes,” Ms. de Taillac said. “You don’t want the sun to be on your skin, because that’s what makes you hot. If you think about it, you really have to cover yourself to the maximum, but with ventilation.”

Inès de la Fressange, the famously chic model-turned-designer (and former face of France), who was about to head off to St.-Tropez, agreed. “The idea that you have to show your body because it’s warm is not a good idea,” she said.

Each of the women recommended maxi dresses and skirts, with sleeves, rather than cropped tank tops and shorts. Also, loose garments rather than clinging ones. Flat shoes that are not too tight because feet swell in the heat. And nothing that could rub against your skin, including tight armholes, too many accessories or even belts. If you are desperate for a waist, try to find something with elastic.

“My uniform in India is a cotton poplin shirt or shirtdress,” Ms. de Taillac said. If you are concerned about looking as if you’re in a muumuu or portable tent, the key to preserving a neat silhouette, she said, is choosing a dress with narrow shoulders to create a regal line. (See, for inspiration, the many elegant trapeze and tent dresses of Cristóbal Balenciaga.)

For another strategy: “Dare to be simple: simple long skirts, simple long pants,” Ms. de la Fressange added.

Then opt for “quite large things,” she said — especially her favorite garments: men’s cotton poplin shirts. If you have noticed that shirts and shirtdresses seem to be No. 1 on these women’s lists, it is not a coincidence. Button-ups have a crisp integrity and ease that stands up in the heat, not to mention longstanding associations with professionalism that push all sorts of subconscious buttons associated with the idea “pulled together.”

“Sometimes women make mistakes when they buy things in their size,” Ms. de la Fressange went on. But it’s both more comfortable and more fashionable to wear a shirt in a larger size, she said. You could even buy one and wear it as a dress.

Her favorite insider tip, no matter what the season, is to shop in the men’s department. “Don’t go where you are supposed to go in a store,” Ms. de la Fressange said. “I always go to the men’s department. Often the shirts are better quality, and cheaper.”

As to which shirt to choose, she said: “Pale blue poplin. It works for everybody, every age, every color of hair. Everybody’s beautiful with it.”

Your Style Questions, Answered

Every week on Open Thread, Vanessa will answer a reader’s fashion-related question, which you can send to her anytime via email or Twitter. Questions are edited and condensed.