Workers place sandbags in front of the entrance to Faneuil Halll to prevent further flooding during a storm in Boston on Friday. (Adam Glanzman/Bloomberg)

The monster came right back.

For the second time in weeks, Boston and scenic shore communities were lashed by a hundred-year storm. It left little doubt to some that near-hurricane-force winds that drive freezing floodwaters into business districts and neighborhoods are becoming a new normal for which the city and its surrounding area are not prepared.

In other words, impacts from climate change, which were supposed to wallop the area 80 years from now, are already menacing a region that is only beginning to talk about ways to protect itself.

Boston city officials, along with civic and business leaders, are seriously considering building a barrier in the mouth of a harbor lined with commerce to protect it from storm surge and sea-level rise. And they are examining islands in the harbor that act as buffers against surging tides, studying whether they can be enlarged.

The state of Massachusetts is also making moves to protect communities, talking with local leaders about sustainability projects against what residents of Scituate and other coastal towns endured Friday and Saturday — icy water at their doorsteps, running clear and braided through the streets as if in a bathtub.

“There are little pieces of [an amelioration plan] coming,” said Kathy Abbott, president and chief executive of Boston Harbor Now. But at the moment, it’s all just theory.

“The big question is how do we get organized to implement this and how do we pay for it,” said Abbott, who sits on the city’s Green Ribbon Commission of elected officials, planners, developers and conservationists.

Abbott believes the back-to-back monster storms have gotten everybody’s attention and might finally make climate resilience a top priority. “I think it does,” she said. “Now that we’re having these hundred-year storms every two months . . . it’s providing a sense of urgency without a [tropical storm] Sandy or another horrible storm.”

Gov. Charlie Baker (R) declared a state of emergency over the weekend, and on Sunday, as more than 166,000 electric customers remained without power, he toured some of the hardest-hit areas along the shore, both north and south of the city.

Despite the risks, Boston approved a 1.3 million-square-foot mixed-use development in one of its most vulnerable areas, the tony Back Bay, where three feet of sea-level rise — one of the more conservative estimates for the amount of water that will creep in in the next 40 to 100 years — will drown homes and hotel entrances along the harbor.

The billion-dollar project will top and surround one of the city’s busiest commuter stations. As of now, there are no laws requiring developers to adapt to climate change, Abbott and others said. Developers are implementing some protections, she added, but it’s all voluntary.

Elected officials catch much of the blame for the failure to have protections in place, but Deanna Moran, director of environmental planning for the Conservation Law Foundation in Boston, said that’s not entirely fair.

“It’s not the just city or state leadership, we also need leadership from developers,” Moran said. “Some of the easiest things we can do is leverage the system we already have.” For example, she said, developments could include lush gardens that suck up rain in soil rather than allowing it to run into streets.

Moran also envisions building wetlands in huge open spaces to capture invading water. “We operate under the notion of sea walls and hardening surfaces, but there’s nothing we can do to completely keep the water out. We have to adapt to let the water in when we have storms like this” and sponge it into the earth.

Boston-area and state officials deserve credit for talking things through, but “at this point these kinds of storms are very much foreseeable,” Moran said. “What we’re doing today is acknowledging the risk and talking about what we need to do to prepare, but we’ve done little.”

Lack of preparation is a refrain that echoes up and down the Atlantic coast, with cities getting wake-up calls from catastrophes. In the summer and fall, Florida’s unprepared southern tip and the Sun Coast off the Gulf of Mexico faced down two hurricanes, flirting with disaster.

Miami flooded. Naples was wrecked by wind and rain. The Tampa Bay area narrowly averted the Category 3 storm that planners and other experts say could wipe it out, costing $175 billion in estimated damage and dozens of lives.

Nearly 1,500 miles north, Boston has a similar dilemma. Like much of Tampa and St. Petersburg, a third of the city sits on silt. Almost as soon as settlers arrived in the 1600s, they started stretching out the city’s boundaries with fill.

Global warming that’s causing the ocean to expand could send the sea back to reclaim it.

“Boston will return to its historic boundary lines,” said Emily Norton, director of the Massachusetts chapter of the Sierra Club and a city councilor in Newton, west of Boston. Talk and theories tossed around at a commission meeting won’t stop it, she said.

“You see the talk, but you don’t see the action,” said Norton. “They’re talking about spending billions of dollars for a sea wall and dikes, hardening the shore. Boston should be doing more. Massachusetts is a state that others follow, and Massachusetts has to do more. We have to take steps to reverse this and get off of fossil fuels.”

Emissions from fossil fuels, such as oil and coal and, to a slightly lesser extent, natural gas, create carbon pollution that forms an invisible ceiling over the atmosphere, trapping heat that warms the globe.

“People have been shocked,” Norton said. “The storms we’re seeing now, people thought this was decades in the future.”

She recalled a vision from the last storm: a resident filming a large dumpster floating down a Boston street like a child’s rubber duckie. “It’s crazy. It’s happening much faster than people expected.”

So why haven’t the city and state taken stronger action? Norton sighed, struggling to find an answer. “There are people with emphysema who keep smoking,” she said. “Human nature is such that we really need the two-by-four between the eyes.”

Like the March storm that followed the January storm, that jolt could be just weeks away, Norton said.

“The longer we wait, the more expensive it is to solve. The more difficult it is to solve, the more destruction we’re going to be seeing,” she said.