Mayor Eric Adams was blasted for a slow response to Friday’s massive flooding — after he failed to issue more than the most meager warning the day before and even showed up late for an emergency management hearing with other officials.

While other leaders from organizations such as the MTA held major briefings Thursday, Adams’ administration only retweeted a few weather announcements — he then went off to a party at a fundraiser that night, leaving classes to go on as normal at schools, some of which wound up flooded.

He finally issued a state of emergency some two hours after Gov. Kathy Hochul said she planned to order one for the state on Friday — and as rain started to taper off.

By that point, dozens of streets throughout the city were flooded and subway service was down or delayed across the board. 

Even fellow Democrats were left steaming.

“I am dumbfounded by the lack of communication from City Hall to prepare people for this extreme weather event,” Councilman Lincoln Restler (D-Brooklyn), who represents Brooklyn Heights and South Williamsburg, told The Post.

“Aggressive, early communication and to plan for the worst-case scenario … Neither happened here.”

Follow along with The Post’s live blog for the latest on the torrential rain flooding NYC

“Hosting an emergency press conference about a storm after the storm had passed was not the best strategy,” another city lawmaker quipped. 

Adams’ first comment on the storm came at about midday, warning people to stay home after hundreds of thousands of school kids had already headed out to class.

“If you are home, stay home, if you are at work, shelter in place for now,” said the mayor, who arrived 40 minutes late to his press conference with Hochul and city and state agency heads.

The declaration came hours after weather experts said it was clear that the rain would create serious and possibly deadly conditions.

“There were already significant road closures and ponding of water and standing water on our roads in the 5 a.m. hour,” Accuweather director of forecasting Dan DePodwin told The Post.

“The really significant issues began starting in the 5 and 6 a.m. hours this morning, and then it just ramped up from there.”

Forecasters warned the Adams admin of the catastrophic potential of the rainfall more than a day ahead of time.

The National Weather Service issued a dire update by 8:30 a.m. of flooding already underway that the agency described as “life-threatening” by 10:45 a.m. — yet the mayor had yet to tell residents to stay inside. 

“A State of Emergency should have happened at 5 a.m.” city teacher Shatasia Frazier railed to The Post.

“Nothing was handled. He should have shut everything down. Did you see the videos? It’s disgusting.”

“You did a hot mess,” the pre-K teacher fumed. 

Another 26-year-old teacher said Adams’ actions were too little too late. 

“By the time he put the emergency out people were already on their way to work,” Tiara said.

“It’s a disservice to the people on the front line.”

The foot-dragging by Adams also got him dragged online.

“Like many New Yorkers, our member’s homes are flooding RIGHT NOW,” New York Communities for Change tweeted.

“Where is Eric Adams??? And why is he attacking the city’s climate law??? Why does he oppose taxing the rich so we can fix infrastructure???”

X user @IanMacAllen posted a “Where’s Waldo” image of the mayor at about noon with the comment: “Has anyone seen Eric Adams since Brooklyn started flooding?”

This wasn’t the first time Hizzoner faced backlash for failing to quickly respond to an emergency in the Big Apple. 

When “dangerously high levels of wildfire smoke” filled the air back in June, New Yorkers were largely caught off guard with their mayor MIA on messaging.

“From orange skies to flooded streets, a pattern is becoming clear – the administration has been delayed and insufficient in using the most effective tools in notifying New Yorkers about extreme weather emergencies which are only increasing in frequency,” Public Advocate Jumanne Williams said Friday. 

Also, Last December, when a once-in-a-lifetime storm flooded the city — Adams jet-setted to the US Virgin Islands for a two-day vacation. 

City Hall defended the Adams administration’s response, which relied on social media and city alerts to inform the public on Thursday and Friday.

Adams’ spokesperson Fabien Levy said the decision to issue a state of emergency was made hours prior to the announcement, but it remained unclear why it wasn’t made public.

City Hall did not immediately respond to a series of questions from The Post.

By late Friday afternoon, the mayor went on a media blitz where he said if someone was caught off guard by the flooding that’s on them. 

“If anyone was caught off guard, they had to be living under a rock,” Adams said on 1010Wins. 

As the storm approached, Adams held a swanky birthday fundraiser Thursday evening at The Hudson NYC, where the suggested contribution was $2,100, according to the invite.

Other New York City leaders were irate over the administration’s response — or lack thereof.

Brooklyn Borough President Antonio Reynoso called on the city and state to revamp their messaging when it comes to severe weather.

“This morning’s events have made it glaringly apparent that New York City and State must improve their processes for communicating with New Yorkers about sudden and extreme weather before it happens,” Reynoso said.

One of the City Council members was even caught off guard by the disruption caused by the rain on the subway system, sharing on social Friday afternoon she had been stuck on the subway for hours. 

“I have been on #2 train at W 96 St station for hrs & I am not alone!” tweeted Gale Brewer (D-Manhattan).

Hochul defended Adams when asked about the mayor’s slow response on CNN saying her office has “been working closely with New York City.”