As the summer brings sweltering heat, office dress is shifting. Skirts and sleeves are shorter, sandals are prevalent, and both seasoned professionals and the summer’s crop of interns test the boundaries of casual dress.

But as office dress codes become more relaxed, some employers worry that the work ethic will weaken. Will wearing polo shirts to the office discourage employees from staying past 6 p.m.? Will dressing in khakis instead of a power suit make a manager less likely to invite clients to lunch? Will wearing sandals lessen someone’s motivation to negotiate a deal?

Business consultant Andrew Jensen, who has studied the correlation between office workwear and productivity, says that just as managers disagree on the issue of attire, there also has been a lack of consensus among researchers: “It comes down to office environment. In a more relaxed environment, casual dress works and doesn’t have much impact. In a more traditional environment, casual dress does have an impact, especially when employees go too far.”

Jensen of the Sozo Firm in Pennsylvania says that in some workplaces, bosses contend that the national trend toward business-casual wear can boost morale and camaraderie and even increase creativity by allowing workers to feel comfortable and happy. In others, supervisors say that business-casual can easily be abused and lead to sloppiness, laziness and a decrease in professionalism. “The dress code really needs to be customized depending who your customers are and how often you interact with them,” Jensen says.

On a given day, what we wear to work can affect our focus, motivation and what we accomplish, says Mike Slepian, adjunct assistant professor at Columbia Business School and author of “The Cognitive Consequences of Formal Clothing.” He says casual clothing makes workers think less abstractly and more concretely — useful for completing tasks focusing on details such as writing code or planning a product launch. He says that with formal dress, workers feel more powerful and ready to tackles higher level abstract thinking. He says that when workers need to think creatively about the bigger picture, that’s when dressing formally will increase productivity.

In offices that have Casual Fridays, some employees see their mood shift with the change in work attire. Georgi Pipkin, corporate manager of marketing at Baptist Health South Florida, dresses for the interactions planned for the day and finds that her outlook correlates with her clothing: “If I’m wearing jeans on a Friday, I have a more relaxed, less stressful day. If I’m wearing a dress, I might be meeting with a vendor and there’s an expectation that I’m going to perform at a different level.”

While industry, geography and job title play a role in dress code, overall workplace attire increasingly has become more relaxed. Pantyhose are out, the once de rigueur suits are rare, and polo shirts have replaced ties. The movement toward business-casual is spurred in part by the influx of millennials in the workforce who prefer to dress down, according to Office Team, a national staffing service. “Millennials have seen Mark Zuckerberg in his T-shirts and jeans, and they believe what you wear does not define how successful you are going to be or whether it will impact business,” says Angie Diaz Medina, director of culture and patient experience at Baptist Health South Florida, which has implemented casual day on Fridays. “Dress is only one piece of culture, but it really shows employees where the company mind-set is.”

According to the Society for Human Resources Management 2015 Employee Benefits Survey, 62 percent of businesses nationwide allowed casual dress once a week, while 36 percent allowed it every day — a notable increase from the 2014 figures of 56 and 19 percent, respectively. Even the most traditional industries are shifting toward more casual dress. Banking giant JPMorgan Chase & Co. now lets workers wear business-casual clothing most of the time as does accounting firm PricewaterhouseCoopers, which asked its people to consider what they are doing each day, with which clients, and dress in a way that reflects that.

Conservative businesses that have relaxed their dress code see the results. Dorothy Eisenberg, a partner in Miami’s Gerson Preston, says the transition into business-casual at her firm has created a workplace culture that attracts young workers, the lifeblood of an accounting firm: “It shows that we are not stuffy, that we are complying with what the market is like, and that our people are more relaxed and happy.” Eisenberg believes the positive atmosphere leads to happier clients, too: “When the morale is high, it affects productivity.”

However, pushing the boundaries of business-casual too far can be problematic in any workplace. As a corporate trainer and Dallas-based business coach, Shontaye Hawkins works with companies across the country and suggests they provide employees photos of exactly what they consider business-casual. Dressing too provocatively or too casually can adversely affect the employee and employer, she says: “When you wear flips-flops and shorts, you become less focused on work. It’s like you can’t wait to get off, and you’re thinking about everything outside of office versus work that needs to get done.”

Even more, dress affects external perception. “You don’t want to lose a potential client or customer because they come on a day someone is wearing flip-flops and decide your workplace is unprofessional,” she says. “Dressing too sloppy can cost a business money.”

Some employers give their employees leeway to dress up or down, asking mostly that they “be presentable” in the office. At the Miami law firm of Kluger Kaplan, lawyers often walk the hallways in nice jeans and a button-down shirt. But when they go to court, Alan Kluger urges attorneys to dress the part and insists it creates confidence and creditability: “If you’re in front of a jury, you want to be the lawyer they want to hire. Dress makes a difference in the courthouse, it just does.”

As Jensen notes, there is no perfect way to predict how implementing a dress code in your workplace will affect productivity. However, when workers have the flexibility to wear what makes them look and feel good, they tend to approach work more confidently. “We are seeing more relaxed dress in every aspect of American life,” Jensen says. “But it’s still about trust. You want to dress in a way that people trust you.”