In fact, when the temperature is around 30 degrees, the coat becomes a woman's most important fashion accessory. Obama could have worn a burlap sack underneath because what was on top was delightful. Other notables: Jill Biden's Lela Rose metallic trench with a distinctive bow; the black-and-gray coat with a brooch and silver scarf worn by Myrlie Evers-Williams, who gave the invocation; Sasha Obama's iris wool coat by Kate Spade New York; and Malia's purply-pink J. Crew coat.
More from J. Crew: Obama's hot pink-almost purple leather gloves and light-blue pumps. Yet the very prepared (and smart) woman switched into a pair of navy suede boots with smooth-leather toes by former Coach designer Reed Krakoff for the long, and chilly, day ahead.
Under her coat, Obama wore a Thom Browne A-line dress with navy-blue piping against a patterned loden, pink, and white triangle print. Over the dress, she wore a navy cardigan. She appeared fresh in her new bangs and long lashes.
The overall look was soft yet powerful, feminine but with a couture menswear feel. It was simple, yet royal.
Browne may not be a household name, but 12 years ago, he introduced his signature men's suit - flat-front pants that stop at the ankles and two-button jackets that stop at the wrist. Shrinking the classic, boxy silhouette effectively forced men to change the way they thought about fit. When he launched his women's-wear line in 2010, the silhouette dominated those tailored pieces, too.
It makes sense that Obama likes Browne's work - she wore a Browne piece to the Democratic National Convention as well as to one of last year's debates - because she embraces unconventional cuts. Some call her the first lady of the too-high waistline. But it's her somewhere-between-empire-and-the-natural-waist that makes her look so fashion forward.
In fact, it's that twist on classic pieces that makes them modern, whether her boatneck is off-center or her pants stop at the ankle.
"I thought the lines on that coat really flattered her figure," said Clara Henry, director and chair of the department of fashion design at Philadelphia University. "The patterns worked well with the eye and it texturally all went together. The pieces were individual, but there was a wholeness to it."
Obama's coat was fashioned from a silk jacquard, the same kind used in a men's tie - a nod both to mixed media and her ability to blend roles as first lady, mom-in-chief, and no-nonsense activist.
As a family, the blues and purples made the Obamas look majestic, even subdued. And their rich-hued coats were statement pieces, unlike the candy-colored outerwear that merely complemented the dresses they wore four years ago. Back then, Michelle Obama's lime-green suit by Isabel Toledo said "We're new." This year's blues and purples - historically the colors of royalty - send a message that they've settled into their roles.
Speaking of blues, this weekend the Obama women also wore shades of blue - in the Blue Room of the White House, where the president was officially sworn in Sunday. The women wore contrasting tights and gloves, so the simple cuts and deep colors popped with pizzazz.
"I do think the whole, overall tonal blue was really nicely done," Henry said. "There was a serenity and a calmness."
Contact fashion writer Elizabeth Wellington at 215-854-2704 or email@example.com. Follow her on Twitter@ewellingtonphl.