Forget about waiting for the weekend to cut loose. Midweek is heating up as a popular date for parties, as demonstrated by a slew of Wednesday and Thursday soirées last week in New York. While temperatures climbed into the 80s, celebrities and social types celebrated at fashionable events all over town.

On Thursday, Elizabeth Hurley took over Saks Fifth Avenue's second floor to present her new swimwear line to a ladies-who-lunch crowd that included Iman, Dr. Lisa Airan, and Marjorie Gubelmann Raein, as well as Elton John. The model-turned-actress-turned-designer's skimpy bikinis were a blunt reminder that bathing suit season looms. Hurley herself refused the pasta, salad, and crab cakes on offer and opted instead for a glass of white wine. "Can I do that?" she wondered aloud, before suggesting her swim accessories—a see-through tunic and her trademark white stretchy pants—for when "you're having a day where you want to cover up your tummy or your bum."

The previous evening, editors, models, and musicians gathered in a four-story tent in blooming Central Park to preview 150 looks from H&M's fall collection. Sweden's cheap-chic giant spared no expense (reportedly, $7 million) to accommodate 800 guests. After dining on beef and lobster, revelers enjoyed a short set by Miri Ben-Ari, John Legend, and an energetic Kanye West. Catalina Sandino Moreno, who in February was front-row at Calvin Klein, revealed, "My first summer in New York, I shopped at H&M. In Colombia, there are no seasons, so I really needed new clothes."

Meanwhile downtown, Hollywood heavyweights gathered at the State Supreme Court house for Vanity Fair's annual party to kick off the Tribeca Film Festival. Editor Graydon Carter's überswanky gala drew Nicole Kidman, Willem Dafoe, Christopher Walken, and Kevin Bacon. Later, Padma Lakshmi and Carlos Miele bonded at the after-party they threw at artist Hunt Slonem's West Side loft. The hush-hush invite lured the likes of Robert De Niro, his wife, Grace Hightower, Gina Gershon, and many a Miele-clad beauty.

—Sarah Cristobal