She was born at Dalkey, Ireland, daughter of Peter White, the head of the Irish Wool Manufacturing and Export Company, and his wife, the former Annie Mayne. Carmel White moved with her family to the United States as a child, after her father's death, when her newly widowed mother was called upon to replace him as the head of the Irish pavilion of the Chicago World's Fair. Carmel had several siblings, including Victor White, a painter who decorated the Roof Ballroom of the St. Regis Hotel, and Christine (White) Holbrook, who became the editor in chief of Better Homes and Gardens. She also three additional brothers, Thomas Justin White, Peter Desmond White and James Mayne White.
Carmel White married a prominent society lawyer, George Palen Snow, in 1926 and had three daughters—Carmel, Mary Palen, and Brigid.
After working briefly at T.M. & J.M Fox, a famous dressmaking concern in Manhattan that was owned by her mother, Snow went to work as a fashion editor at American Vogue in 1921 and joined Harper's Bazaar 11 years later. She famously described her goal at the latter publication as creating a magazine for "well-dressed women with well-dressed minds". Her influence at both magazines went far beyond fashion reportage: she brought cutting-edge art, fiction, photography, and reporting into the American home.
Snow was particularly gifted at discovering new talent, as well as fostering new avenues of exploration among previously-established artists. In the 1920s, she worked closely with Edward Steichen, already a world-famous photographer, helping him to apply his talents to fashion photography, which he did to great effect, well into the 1930s.
In 1933 she hired Martin Munkácsi, the great Hungarian photojournalist, to take his first fashion shots; she brought him and the socialite-model Lucile Brokaw to a windy, autumnal beach and, in the course of an afternoon, Munkácsi created history by coming up with the first fashion photographs shot outdoors and in motion—a revolutionary act.
Snow hired her famous art director Alexey Brodovitch on the basis of an exhibition of his work in graphic design, and found her fashion editor, Diana Vreeland, after noticing her, with her inestimable chic, dancing across a crowded room. The three of them, Snow, Brodovitch, and Vreeland turned Harper's Bazaar into the most admired magazine of the last century.
She played a key role in discovering the American fashion photographer Gleb Derujinsky, encouraging him to travel around the world and explore his more adventurous artistic ideas, such as shooting on top of Nemrud Dagh Mountain in Turkey. The models were usually styled by fashion editor Diana Vreeland in expensive gowns, creating a dramatic contrast to the diverse backgrounds of the photographs, which included deserts, junkyards of cars and airports. Derujinsky was interested in the entire picture, paying as much attention to the scenery as the model and the fashion, rather than restricting himself to studio shots.
Among the now-household-names whose careers Snow encouraged are: Andy Warhol, Maeve Brennan, Louise Dahl-Wolfe, Truman Capote, Jean Cocteau, Cecil Beaton, Christian Dior (his 1947 debut collection she dubbed the "New Look"), Cristóbal Balenciaga, Carson McCullers, Kenneth Tynan, and numerous others. She also discovered Lauren Bacall and put her on the cover of Harper's Bazaar, an act that brought the unknown model to the attention of Hollywood.
Snow once famously said that "Elegance is good taste plus a dash of daring." She lived that saying in every aspect of her professional life, until her forced retirement from Bazaar, when she was in her seventies. Her position as editor in chief was taken over by her niece Nancy White. She died in New York City, New York.
As to why her reputation faded, while Vreeland went on to become a legend, photographer Richard Avedon (quoted in A Dash of Daring: Carmel Snow and Her Life in Fashion, Art, and Letters, a biography by Penelope Rowlands that was published in 2005) said: "She was older, right? And she died before stardom was the thing". He added, however, "Carmel Snow taught me everything I know." Many others, and particularly photographers, also credited her with helping them to hone their craft. Henri Cartier-Bresson, with whom she worked closely, beginning in the 1930s, described Snow as "magic". And when the great Hungarian photographer known as Brassai heard of Snow's retirement, he was said to have abandoned photography for good.