H e does not fear Sunpocalypse. He’ll laugh if you call it that. He does not shop on London’s Savile Row, but his stiff upper lip makes it seem so. He does not begrudge his uniform. He relishes the corporate noose. He admires, never envies, a woman in a red tank top. He does not hog the Metro fan.

His cuffs stay buttoned. His jacket, unruffled. His handkerchief, his only shield.

Washington men do not bow to Apollo. Our sun kings never relinquish the suit.

“This is my first week of work,” said Sebastian Hill of the Securities and Exchange Commission. “The suit will impress my bosses.”

Do sweat stains?

“Well, the suit matters a great deal.”

So Hill, like thousands of young guns every summer, blends into the swarm of Washington veterans who don head-to-toe navy or black suits, the professional equivalent of war paint.

But Friday, heat was more than nuisance, with Washington’s heat index well over 100 degrees by 9 a.m. and life-threatening temperatures looming over most of the country. The gentlemen of more practical cities — Dallas, Atlanta, New York — renounced formality to save their bodies and dry cleaners from misery.

“Most of the financial firms have lightened up on dress code,” said Glenn O’Brien, GQ’s Style Guy columnist and author of “How to Be a Man: A Guide to Style and Behavior for the Modern Gentleman.” “The only people wearing suits in New York today are the lawyers that are going to court.”

Not Washington men. “If you can’t stand the heat, get out of the kitchen,” muttered Sen. Harry Truman in the 1930s, most likely in July. Politicos still live by that motto. When tempers and temperatures hit boiling points, this breed of Washington suit stays strong and steadfast — at least until August recess.

But New York, a city with a climate and professional culture not unlike the District’s, caved to the sun in the past few years.

“I think most men here know if you dress for the weather, it shows that you have common sense,” O’Brien said. “People are looking for that in management, maybe not in politicians.”

So maybe Beltway critics are correct to call the politicos out of touch. They’re certainly not in touch with their own thermoregulation. But that’s because on Capitol Hill, will trumps weakness. Ideals stay stringent, even when impracticality could cause heat stroke or malodorous scents to rise from one’s wool blazer. The congressional dress code has always been a brotherly code of honor, adopted by all ages and species of homo politicus.

Congressional offices, a sample of which would not comment formally on their business-formal dress codes, don’t appear to have budged on their sartorial expectations, even for a daunting heat wave or sweat-inducing debt-ceiling talks.

“There was no change in dress code in my office,” said Zach Dann, a Senate staffer who, after only four weeks in Washington, calls the suit “standard operating procedure.”

Others echoed the sentiment.

“We have bow-tie Friday, not casual Friday,” said Chuck Roberts, a staffer in Sen. Patrick J. Toomey’s (R-Pa.) office who copes with the heat by leaving his jacket and tie at the office.

Perhaps that’s because the suit, whether bespoke or ill-fitting, has long been the hallmark of Washington culture.

“For a lot of men in D.C., wearing a suit is a point of pride. It implies you’re doing something important,” said Chris Hogan, founder of District-based menswear blog Off the Cuff (Offthecuffdc.com). “The suit will always matter here, especially when things are in political or economic turmoil. People look for stability, and the suit is the ultimate mark of authority. Can you imagine the president coming out to talk about the economy in khakis and a golf shirt?”

Hogan noted that the suit is not restrictive in itself but that men wear the wrong material during record-setting heat waves. “A lot of men don’t know their options. If you wear a suit that’s great for November in August, you’re going to be uncomfortable.”

But not all men clung desperately to their blazers and handkerchiefs. A few envelope-pushing, sartorially progressive transplants wore lightweight seersuckers and linens, appropriate attire for code-red air.

“I’m from Texas,” said Jeff Sell, vice president of the Autism Society, wearing a thin khaki summer suit at Union Station on Friday morning. “Business casual is standard there, and men have also adopted the summer suit in Texas. Yo u can wear jeans and a blazer to work, but a lightweight suit is actually more comfortable.”

Others reject Washington’s sweat-it-out culture, refusing to challenge the morning sun before they challenge the opposing parties.

Brian Prokes, a House staffer, combines his exercise regimen with his commute, walking almost two miles to work in University of Florida athletic gear, hanging his full suit on his backpack, with Mother Nature as his steamer. “I do this everyday. I had a guy tell me yesterday, ‘Smart thinking, I’m going to do that tomorrow.’ ”

House staffers are lucky to have shower facilities nearby at the congressional gym. And some members of Congress have private showers in their offices.

Retail experts agree that Washington is forever attached to its sweat-stained suit, but it should amend the uniform to include cooler fabrics or forgo the tie.

“We’ve had customers shop with us for over 30 years, and every year, they’ve bought a variation on the summer-weight wool suit,” said Liberty Jones of Neiman Marcus at Mazza Gallerie. “But with seersucker and madras coming back into style, some men are becoming more, I guess you would say, progressive with their suits.”

O’Brien prescribed a more traditional fix: “We need to go back to the days when senators wore panama hats and white suits. Politicians shouldn’t be sweating. It makes them look untrustworthy.”