On the official first day of summer, we thought you’d like some tips to beat the heat while continuing to dress professionally for work. A late-’90s survey of 500 businesses showed that relaxed workplace dress leads to relaxed manners, relaxed morals, and relaxed productivity. Now less than 10% of Fortune 500 companies allow business casual dress, down from more than 50% a few years ago. (For information about how to adjust your company’s dress code, come back next week.)

If your company still allows business casual, you may want to take it up a notch nonetheless. According to a survey by the Ladders executive search firm, 60% of managers thought employees in more formal business attire were likely to be taken more seriously– and 22% of managers admitted that better dressed employees were more likely to get promoted. Jean shorts in the workplace certainly don’t project the “Here I am! Promote me!” image, but a sweat-soaked suit is neither attractive nor comfortable. It’s important to find styles that look respectable but can keep you cool. Workplace dressing tips for women will be published tomorrow.

These summer dressing tips are from Nancy Nix-Rice, president of First Impressions Image Consulting and co-author of The New Professional Image. The tips are based on a corporate atmosphere, so adjust them according to your work situation.

1-I’m sorry to say it, but there is no such thing as a short-sleeved business shirt. In casual working environments, a short-sleeved knit polo or sport shirt is fine, but if the shirt is accompanied by a tie, long sleeves are a must, no matter what your job is.

2-Under a jacket, a quarter-inch of sleeve should always show at your wrist, below your jacket cuff.

Darker colors absorb light and make you feel hotter, so consider trading your black polo shirt for a midtone color or substituting a lighter grey suit for your typical charcoal.

3-In the South, khaki suits can even be appropriate for work, although seersucker suits are only acceptable in the most tropical climates. Lighter color suits will also give you a more summery look.

It’s counterintuitive, but 100% wool suits can be great in the summer, since wool is a natural fiber that lets air in and out. Most synthetics won’t do that (although microfiber does). Smooth textured Super100 and Super120 wool suits have very fine threads, so they’re lightweight. Wool with brushed texture, like flannel, is too wintry and hot for summer wear.

4-You tend to get what you pay for with suits, so consider investing in classic conservative ones, such as American Made Suits from Hart Schaffner Marx.They won’t go out of style, wear well and long, and if you choose color and fabric carefully, can be worn year-round.

5-Even if you need a suit jacket for meeting with clients during the day, you can hang it up while you’re in your car or in your office. That way it’s there when you need it, but it’s not keeping you hot.

6-Cotton undershirts provide a cool, absorbent layer. But if you’re wearing a sport shirt with the top buttons unbuttoned, make sure your underlayer is a V-neck. While younger crowds think it’s hip for that little triangle of undershirt to show, older businesspeople (i.e., your boss and your clients) see it as your underwear showing.

7-Another way to keep cool is to have your shirt heavily starched, so it stands away from your skin a bit.

Heat and humidity can wrinkle a pair of cotton khakis in no time flat. Khaki colored microfiber trousers are wrinkle-free and breatheable.

8-In even the most casual workplace environments, too much bare skin is professional exposure of the wrong kind. So save the shorts, cut-offs, and sandals for weekend wear or the company picnic. Even at a company trip to the baseball game, true casual wear is often inappropriate.

9-Leather uppers and soles are more breatheable than synthetics — they’re more natural, so they won’t trap sweat. Woven leather loafers may also allow heat to escape more easily.

Looking professional at work should still allow you to look seasonal. For everywhere but the boardroom, shirts in non-traditional colors are perfectly acceptable alternatives to white and blue, even with ties.

In more casual business situations, a cotton tie is an acceptable substitute for a silk one. A madras tie, for example, can give a summery look.