As if that were not enough, even as he rushed from meeting to meeting and aides hurried to hook up phone lines and computers in a quiet City Hall, the new mayor had to contend with a growing political headache: lingering questions over the treatment afforded to his predecessor at the inaugural ceremony the day before.

Mr. de Blasio said he had no qualms about the harsh words directed at former Mayor Michael R. Bloomberg by several speakers who stridently criticized Mr. Bloomberg's policies and referred derisively to a perceived emphasis by his administration on luxury developments and sports arenas over the interests of working-class and poor New Yorkers.

"I'm very comfortable with all that was done," the mayor said at a news conference, hours after a top Bloomberg aide had suggested that Mr. Bloomberg's tenure had been unfairly characterized.

Amid all that, Mr. de Blasio found himself dependent on several key holdover appointees from Mr. Bloomberg's staff, including the fire and sanitation commissioners, whom he charged with overseeing the city's defenses against the storm — a potentially defining moment in the infancy of his administration.

If Mr. de Blasio sounded confident as he defended his inauguration, his voice was less firm as he ticked off the scores of snowplows and salt spreaders mustered against the approaching winter weather in his first official question-and-answer session with reporters.

There were signs aplenty that the new mayor was still becoming accustomed to the trappings and traditions of being one.

As he swore in William J. Bratton, his new police commissioner, at Police Headquarters, Mr. de Blasio also said he was getting used to referring to his wife, Chirlane McCray, as the first lady.

"I find it a little formal," the mayor said with a laugh, "but I'm going with it."

Running through the revised alternate-side-of-the-street parking rules, he lamented that he could no longer drive himself to work in the mornings.

Even Mr. de Blasio's children, accustomed to the spotlight after being featured in his mayoral campaign, received an early lesson in the level of scrutiny that first families must face.

An online message emerged at midday showing Mr. de Blasio's teenage son, Dante, a public school student, responding to a friend who asked him if classes might be canceled on Friday.

"Old man winter will decide," Dante wrote in a message that spread quickly on social media, but that he was trying to "convince my dad." Aides to Mr. de Blasio had no comment, but, later on Thursday, Ms. McCray posted a photo of a shovel to her Twitter account, along with the caption, "What Dante will be doing if he does not go to school tomorrow."

But the most visible change from the Bloomberg era, at least for many everyday New Yorkers, came when the mayor presided over his very first emergency storm briefing — a staple of the job and a widely televised chance for a leader to appear reassuring and in command.

Mr. Bloomberg, a former chief executive, took a no-nonsense approach, delivering clinical instructions in the voice of a father instructing his children.

Mr. de Blasio put his own spin on the genre, opting for a warmer, more personal touch, much in keeping with the populist tone of his campaign.

He referred to his commissioners as "a dream team," declaring they could "take on any storm, anywhere."

He declared, "We are ready for whatever hits us," but also confided that he would feel "a lot calmer when the storm system flows out to sea, I'll tell you that much."

Mr. de Blasio also touched on his usual themes of a united city, urging citizens to "look out for your neighbors" and for people who are homeless.

And at one point, barraged by questions about storm preparation, Mr. de Blasio lapsed into a soliloquy whose existential tone and preacher's rhythm. "We know that the number of inches may go up or may go down," he said. "We know the winds may be stronger or weaker. But we know we have to be ready."

Mr. Bloomberg, although he was scheduled to be in Hawaii on Thursday, still loomed large over the day's events.

One of his chief aides, Howard Wolfson, appeared on CNN and WNYC radio to say that some of the remarks at Mr. de Blasio's inauguration, including by the singer Harry Belafonte, had unfairly characterized the departing mayor's record.

Asked on Thursday about "anti-Bloomberg" remarks at his inauguration ceremony, Mr. de Blasio said he disagreed with the premise.

"I made clear my real respect for Mayor Bloomberg," he said. "It's not a secret that I've had some disagreements with him on policy, but I honored with a whole heart what he did to this city."

Mr. de Blasio said that "everybody who spoke at the inauguration spoke from the heart, talked about their own understanding of our city, and what we need to do to move our city forward."