This Lanvin frock is covetable, but office-appropriate? Not so much. “Pretty dresses work on television or if you’re the First Lady, but they rarely work in an office,” writes The Post’s Katherine Boyle. (Photo by Pascal Le Segretain/Getty Images)

Join us Thursday at 1 p.m. when the Going Out Gurus are joined by The Post’s Deal Hunter columnist Katherine Boyle to discuss the art of looking cool in the summer. Of course, the rest of the Gurus will be on hand to take all your usual going out questions. Submit your questions early here. Get a better sense of Boyle’s take on D.C. fashion and the influence of Michelle Obama below.

GOG: Washington still gets dinged for its fashion sense; our summertime choices certainly would explain why. Some people wear flip-flops to the office; interns have a reputation for showing up the first day in too-short skirts, makeup that’s better suited for clubbing and — I’ve seen this one with my own eyes — midriff-baring tops. What are options right now to look office-appropriate in the heat?

Boyle: Women have it way too easy in workplace fashion, so out of respect for guys, we need to button up. If you’re not feeling the heat in 90-degree weather, you’re dressed inappropriately. Sleeveless sheaths with a white blouse tied over them or blazer are an easy go-to. In the office, women should never be seen in a strapless dress. A sleeveless dress should always cover part of the shoulder. And in the summer, go slightly longer with the hemline. In winter, you can wear shorter skirts with tights, but in summer, when you’re showing off arms, the hemline should be long-ish to give your outfit some balance.

Men and women: Flip-flops are for beaches.

Bottom line: Dress like your boss. If your boss is a middle-aged man and he’s buttoned up in a snazzy suit, you should wear the equivalent. This is especially true for young women: Pretty dresses work on television or if you’re the first lady, but they rarely work in an office. If you’re working in politics, you should wear the elements of the uniform: blazer, pumps, appropriate separates. If you want to dress casually, become a journalist!

Let’s talk off-duty uniforms. In previous seasons, women were hitting rooftop parties, happy hours and weekend festivals wearing rompers and maxi dresses, and so far this year, there has been a fair amount of peekaboo: sheer dresses and cute cut-outs. What trends are you seeing out at bars, restaurants and events that Washington women are doing right?

Boyle: We’re in a best-of-times, worst-of-times scenario this summer. Anything goes, which is great for Washington, but it has to work well: If you don’t have great abs, ignore the midriff trend. Same with the crazy art deco prints: If you look terrible in prints, don’t buy into the trends. Right now, you can wear anything and look “in style,” providing that it fits well.

What should we snag to look cool through the hot days?

Boyle: Pastels. The Candyland palette is in this season, and it’s really easy to pull off. If you’re edgier, buy a sheer blouse or dress and wear it with a slip. Sheer is tricky though, because it rarely works in Washington unless you’re wearing something under it.

You’re a deal hunter: Are there ways to get some of the looks for less?

I haven’t bought retail in years. Thrift stores and consignment shops are the best way to buy quality on a budget. I love Neiman Marcus, but for those of us who can’t splurge every season, it’s better to invest in the unwanted clothes of the women who do shop at Neimans than to buy from fast-fashion chains.

Summer is a conundrum for D.C. men: It’s scalding outside, but some bars will turn away men wearing shorts or flip-flops. Are there any looks that are fashion-forward but still hide the unmentionables? (Feet and legs, that is.) What’s a man to do?

They must suffer. Really, there’s no way around it. I did a piece last summer on “men in heat” and wore a suit and tie to work as part of my research. It’s misery, and I have enormous respect for men coping with the humidity. The only option for men is to wear summer fabrics: no wool! Leave the jacket at work and take an extra supply of shirts to your desk, a la Don Draper. If you have a shower at work, take advantage. And most important tip: invest in handkerchiefs. Not just decorative pocket squares, but simple white handkerchiefs so you can wipe the sweat off your forehead. Most young men don’t carry them, and I guarantee you your boss will be impressed that you’re using a cloth rather than a Starbucks napkin.

You highlighted the broader, political implications of Michelle Obama’s outfits in this story. Do you think her choices have any impact on the fashion of women who work on the Hill?

I do. Many fashion critics will tell you how Michelle Obama has changed the workplace dress code for the better. Women wear color. They wear sheath dresses rather than baggy pant suits. She has perfected her casual, American sportswear look, and it has had a great effect on the work place. The most noticeable change we’ve seen is how casual women look on television. Look at news anchors. Years ago, women in the news wore suits. Now, you’re hard pressed to find a female anchor wearing a blazer. But it’s important to note that Mrs. Obama is serving as first lady, not as CEO or senator. I’m all for women dressing with femininity and style, but I still think women have to respect the history of the suit in the workplace, particularly if you’re not in charge. That means wearing blazers and suits on occasion. The old adage of “dressing for the job you want” still rings true. If you want to be a princess, copy Kate Middleton. If you want to secretary of state, look at the strong women who’ve served in that role. They’ve all perfected their style while serving.