Less than four months ago, Mayor Eric Adams was widely criticized for not giving New Yorkers adequate warning when the city’s air quality worsened rapidly. He shook off the critics, insisting that his administration could not have been expected to do more.

On Thursday, as it became clear that a major storm was about to hit New York, the mayor had the opportunity to take a different approach.

Gov. Kathy Hochul acted first, telling residents to be prepared for flash floods, and warning in a radio interview Thursday evening of “havoc throughout the downstate region.” State transit officials also held a news conference on Thursday to discuss the coming storm.

Mr. Adams, however, did not hold a news conference or address the public until almost noon on Friday after large swaths of the city were already under water and service had been suspended on half the subway system.

By contrast, Mr. Adams attended a campaign fund-raiser Thursday night at a scenic restaurant along the Hudson River in Manhattan to celebrate his 63rd birthday earlier this month. Suggested contributions were listed at $2,100.

His office released its first statement about the storm, a “travel advisory” warning of the heavy rains, via email at 11 p.m. Nearly 12 hours later, just before the mayor was scheduled to address reporters for the first time — and 23 hours after the National Weather Service warned of flash flooding in the city — the Adams administration asked New Yorkers to “stay home if you don’t need to travel.”

Mr. Adams, a Democrat in his second year in office, defended his response at the news conference. He said that “all of the necessary precautions were taken” and that he had relied on members of his administration to alert city residents.

“There was not an absence of a voice of this administration,” he said. Ms. Hochul noted at the same news conference that the storm’s epicenter had by then shifted from the city to the Hudson Valley.

Later, in a radio interview, Mr. Adams curtly suggested that New Yorkers had ample warning of the storm, saying: “If anyone was caught off guard, they had to be living under a rock.”

Mr. Adams received steady criticism throughout the day, with elected officials arguing that an earlier and more urgent warning might have prompted New Yorkers living in basement apartments to seek higher ground or persuaded residents with plans to drive someplace to stay home instead.

Jessica Ramos, a Democratic state senator from Queens and a potential mayoral candidate in 2025, said New Yorkers should have been warned more vigorously. Jennifer Gutiérrez, a City Council member who represents parts of Brooklyn and Queens, said that the city had not embraced the lessons learned from Hurricane Ida in 2021.

Jumaane Williams, the city’s public advocate, faulted the Adams administration for what he called a pattern of “delayed and insufficient” communication.

“I think the city needs to be doing much, much more,” said Shekar Krishnan, a city councilman who represents Jackson Heights and Elmhurst in Queens. “This is a rapidly evolving situation. It’s changing every hour and getting worse.”

Mr. Krishnan said his office was monitoring calls from residents of basement apartments, fearful of a repeat of the deaths that occurred during Hurricane Ida.

“This is just, again, a glaring example of how utterly unprepared we are as a city when it comes to climate emergencies,” he said.

Criticism of the city’s response to a looming emergency was not unusual for Mr. Adams, nor was his strident defense. When smoke from Canadian forest fires blanketed New York in June, neither the mayor nor Ms. Hochul appeared publicly for 12 hours, leaving many New Yorkers unprepared for the dangerously poor air quality.

Mr. Adams asked reporters if he should also be prepared if a “meteor fell to the planet Earth.” A City Council hearing later examined his response to the smoky air episode, and concluded it was sluggish.

Some city agencies did spring into action on Thursday.

Zach Iscol, the emergency management commissioner, said on Friday that he had given two media interviews about the storm the day before, and that the city had sent a flood-watch alert shortly before 3 p.m. via the Notify NYC service, which has 1.1 million subscribers.

At noon Thursday, the Emergency Management Department activated its flash flood management plan, a spokesman for the agency said. In concert with that plan, the Environmental Protection Department cleared catch basins and instructed residents to deploy the 5,000 flood barriers the agency has handed out in the past year.

Other agencies appeared to be responding more slowly. It was not until 10:30 a.m. Friday that the Transportation Department announced a suspension of alternate-side parking regulations, a step typically taken in advance of inclement weather.

Although 150 schools experienced some flooding and one had to be evacuated, Mr. Adams said that school officials had acted correctly in keeping schools open, and not switching to remote learning for the day.

At the briefing on Friday, city officials said emergency workers had rescued people from six flooded basements to that point.

Annetta Seecharran, the executive director of the Chhaya Community Development Corporation, a group that works on housing issues for low-income South Asian and Indo-Caribbean New Yorkers, said the city’s response to the storm had been inadequate.

She said her group had received reports of basement apartments flooding in parts of Queens, including East Elmhurst.

“It’s been two years,” Ms. Seecharran said. “We knew this was going to happen again. There’s absolutely no reason that nothing meaningful has changed. We are in the midst of another serious deluge and homeowners and basement dwellers are still on their own.”

After Hurricane Ida, in which 13 New Yorkers died, Mr. Adams, who had won the Democratic primary for mayor months earlier, expressed shock that he had seen flooding in inland parts of Brooklyn. He said the city needed to “think differently” about how to respond to the effects of climate change.

The administration of his predecessor, Bill de Blasio, said in a report after the storm that the hurricane had been “a frightening lesson in our new reality” and had promised to act “more aggressively than ever to alert New Yorkers to the maximum possible impact.” (Mr. de Blasio was also criticized for being unprepared and slow in responding to Ida.)

“This will mean earlier warnings, more evacuations, and more travel bans — all coordinated by a new senior position at City Hall, the Extreme Weather Coordinator,” the report said.

Emma Wolfe, a former deputy mayor in Mr. de Blasio’s administration, filled that role initially. It was unclear on Friday whether anyone had succeeded her after Mr. Adams took office. The city also vowed to identify all basement apartment dwellers and help them put evacuation plans in place. It was one of dozens of promises contained in the report.

A spokesman for Mr. Adams did not respond when asked how many of the promises contained in the post-Ida report City Hall had fulfilled.