In July 2005, some members of the Northwestern University’s women’s lacrosse team wore flip-flops to meet President George W. Bush. The choice of footwear raised a stir in Washington and beyond. (David Bohrer/Associated Press)

Abra Belke shudders when she thinks about summer mornings in the Rayburn Building. “It sounds like the Four Horsemen of the Apocalypse,” said the former Capitol Hill staffer and lobbyist. “Interns and junior staffers are just clomping down the hall in their $5 Old Navy flip-flops.”

Flip-flops are a fashion don’t for Belke, who writes the Capitol Hill Style blog. But those Hill aides aren’t the only ones flashing their toes. All across Washington, rising temperatures mean a switch to summer styles. And from shoulders to shoes, it’s a moment that tests what can and can’t be worn at work.

For some HR departments, the change of season — and the arrival of a new batch of interns — is an occasion to send friendly reminders about the dress code, which in this city can come with a level of detail befitting the Federal Register.

Others take the approach of one downtown law and lobby firm, which tells its employees to “use good judgment and taste” when deciding what to wear.

“Oh, yes, we have a dress code,” a neighbor told me with a sigh one morning when we were talking about the move from boots to bare legs.

The two-page memo on appropriate attire at the health association where she works is crystal clear on the flip-flop issue. The “summer casual dress code” that takes effect on Memorial Day expressly forbids “rubber flip-flops or any flip-flop style shoe that is audible (slapping against the bottom of the foot).”

In the seasonal office-appropriate-wardrobe puzzle, it could always be worse, at least according to hushed-office-hall legend. I’m told that one august philanthropic foundation with a big office here goes so far as to pronounce that women may wear shoes with open toes, or with open heels, but not both, but it’s not something the foundation has been willing to discuss.

Of course, written dress codes — and those unwritten customs that can loom just as large — apply to much more than footwear. There are policies on spandex, skirt length, spaghetti straps, even socks (at one accounting firm, the guidelines say men should always wear them ).

In some parts of town, like K Street, there are still plenty of suits and ties. “In other places, people dress to impress,” one somber-looking influence-industry pro told me last week. But here, “we dress like we’re going to testify.”

Lots of offices have adopted “business casual” as their year-round look, and some of them break that down in remarkable detail. At the accounting firm KPMG, the “appropriate” list includes “gauchos or cropped slacks if worn with jacket or sweater set.”

Interestingly, skorts and culottes don’t make the business-casual cut at one international law firm’s Washington office. According to the written policy, neither does “anything you would wear to the gym, beach, the park or to clean the garage.” Good to know. (At one environmental nonprofit, T-shirts with logos are off-limits, unless the shirt is making an enviro-friendly point.)

In most of these situations, women have more options than men. But that doesn’t mean it’s easier for women — and many of them complain that, from heels to hemlines, that also means they have more rules to follow.

“This button-down shirt was my attempt to make these pants office-appropriate,” a young woman in a pressed pink blouse and straight pants with a pastel geometric print told me as she and a handful of colleagues ate their lunch one sunny afternoon in Farragut Square.

The downtown trade association where they work doesn’t have a written policy, but there are plenty of lines that can’t be crossed. Heels are frequently expected, but no jeans or denim dresses, they said, and, these days, summer dresses need scarves and blazers to make sure they pass muster.

Men can flirt with questionable warm-weather choices, too.

Ivan Adler, a headhunter who places lobbyists for the McCormick Group, an executive search firm, calls his office dress code “situational attire.” For him, that means occasional Hawaiian shirts in summer, worn with chinos. “They’re nothing unbelievably gaudy that would make someone throw up,” he assured me. “They’re nice. They’re silk.”

But the lines can get fuzzy, especially on Capitol Hill, where old traditions die hard and each member can make the rules for his or her staff.

The Washington Post doesn’t have a dress code. But reporters who cover Congress know that things get serious in the Speaker’s Lobby, just off the House floor, where they can ask to speak with lawmakers.

As the congressional “Guide for Reporters” puts it: “Appropriate attire, such as jacket and tie for men, is required at all times in the Speaker’s Lobby.” (For the record, hats are not permitted).

There are no seasonal adjustments and no precise guidelines for women, and, occasionally, a bare shoulder or exposed midriff has caused a bit of a kerfuffle.

Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington, a watchdog group, remembers being a staff member on the House Judiciary Committee in 1994, when Rep. Jack Brooks (D-Tex.) was its chairman.

Sloan worked for then-Rep. Charles E. Schumer (D-N.Y.), and, she said, “I wore pants. I usually do.” But someone who worked for Brooks approached her and said, “The chairman prefers to see women in skirts.”

She mentioned it to Schumer, and then-Rep. Barney Frank (D-Mass.) overheard the conversation. “In solidarity with you, we should all wear skirts,” Frank quipped. The men didn’t wear skirts, and Sloan didn’t change her style.

At CREW, where she’s in charge, “we’re pretty casual,” Sloan said. “But nobody wears shorts. I think that would be a step too far for me.”

And while she hasn’t opted for a written dress code, she understands why others do.

“My biggest concern has been with interns, who have sometimes come in with remarkably scanty clothes,” she said. (That’s not an uncommon view. Some people really do call them “skinterns.”)

Belke — who has worked for then-Rep. Denny Rehberg (R-Mont.) and the National Rifle Association, but recently moved out of the city to attend law school — said she encourages people who run offices to write down the rules, because it makes it easier to enforce them.

While some of Washington’s written policies can be so precise that they’re silly, it does seem better to be able to say “check the manual” than enter one of those tricky conversations without a bit of paper to point to.

Either way, they’re not easy talks to have. As another working Washington woman put it: “How do you find a delicate way to say, ‘Your skirt is too short?’ ”

Or: “Don’t wear flip-flops, you’re an adult.” The noisy sandals have prompted outrage in the past.

Remember the stir in 2005, when a few members of Northwestern University’s women’s lacrosse team were shod in the rubber sandals during a visit to the White House? But flip-flops are welcome in a few places, including the Washington offices of Quinn Emanuel, a Los Angeles-based law firm where almost anything goes.

These days, Belke says she worries that casual Fridays are emboldening people to wear shorts to work — a no-no in almost any office situation. And she’s had it with people who keep their sunglasses on the top of their head or dangling around their neck, even when they’re not outside. “You’re inside now. You wouldn’t walk around all day wearing your winter coat. You shouldn’t walk around with your sunglasses on.”

In the great flip-flop debate, some fans say the shoes make sense for summer commuting and can easily be slipped off at work.

But Belke isn’t buying that. There are plenty of alternatives, she said, like simple flats. And she’s had the odd experience of sitting in an office lobby and seeing a Hill staffer return from lunch in a strappy summer dress and flip-flops — and then reemerge for a meeting with a jacket and more proper shoes.

“It’s almost like a superhero changing their clothes.”