Hurricane Patricia, which hit southwestern Mexico last weekend, was the largest recorded hurricane to make landfall off the Pacific, but it was not the only historic storm this October. At the beginning of the month, a tropical weather system formed southwest of Bermuda and intensified into a Category 4 hurricane, with heavy rain and surface winds reaching a hundred and fifty-five miles per hour. Meteorologists called it Joaquin, and predicted that the dangerous storm would soon turn northeast. According to their models, New York City and the surrounding coastal region fell directly within the “cone of uncertainty” where Joaquin could make landfall. New York Governor Andrew Cuomo activated the State Emergency Operations Center, and New Jersey Governor Chris Christie declared a state of emergency, warning that major flooding events were likely. No one wanted to be caught unprepared. (Joaquin did turn out to be lethal and devastating–but in South Carolina, where it joined with other storms to cause severe flooding and fifteen deaths, and in the Bahamas, where it slammed several islands and sank a cargo ship, killing all thirty-three of its crewmembers.)

One clear consequence of Superstorm Sandy, which struck the New York City area in 2012, is that everyone, even climate-change deniers, takes planning for extreme weather events more seriously. After Sandy, I reported on why the region’s vital systems for energy, transit, health care, and communications proved so vulnerable to the storm surge. Since then, federal and state governments have spent billions of dollars to rebuild critical infrastructure; hospitals and utilities providers have made major investments in climate security; and “resilience” has become a buzzword in philanthropic and policy circles. Neither adaptation nor resilience is a sufficient response to global warming. Mitigation, which requires converting to an energy system based on renewable resources like sun and wind, is far more urgent. But because the carbon dioxide that we’ve already emitted will produce many decades of rising sea levels, higher temperatures, and more dangerous weather, we have no choice but to adapt. This week, the third anniversary of Sandy, is a fine time to ask what changes the superstorm inspired, and what work remains.

During Sandy, corrosive stormwater quickly inundated the subterranean arteries that connect New York and New Jersey, generating widespread damage and causing years of episodic delays on Amtrak, New Jersey Transit, the Metropolitan Transportation Authority, and the Battery tunnels, as workers slowly repair what is, at best, a woefully inadequate transit system. In New York City, the M.T.A. received four billion dollars in federal money for Sandy recovery and resiliency work, which it has spent on innovative deployable flood barriers, such as the Flex Gate and the Resilient Tunnel Plug, more water-resistant submarine cable, two new pump trains, and structural improvements to the tunnels. But Klaus Jacob, the Columbia University geophysicist who issued prophetic warnings about the city’s fragile infrastructure before Sandy, worries about other openings, “like subway entrances and open-sidewalk ventilation grids.” As he sees it, despite the system upgrades, “most M.T.A. facilities and operations remain vulnerable.”

Jacob is also concerned about the fragile power grid, where breakdowns left eight million households without power during Sandy, some for two weeks. On Long Island, where trustees of the Long Island Power Authority spent just thirty-nine seconds discussing Sandy during a two-hour meeting that took place four days before Sandy hit, and ninety per cent of its 1.1 million customers lost electricity, improving system performance has become imperative. After Sandy, Governor Cuomo vowed to end the “tragedy of LIPA,” and in 2014 the Public Service Enterprise Group (P.S.E.G.) became the area’s main utilities provider. Since taking over, P.S.E.G. has engaged a year-round tree-trimming program to reduce the risk of downed lines, fortified low-elevation substations, updated transmission and distribution systems, and improved its outage-management system. These changes should provide modest improvements, but an energy system that transmits power across wires hoisted on poles that rest beneath trees will always be susceptible to outages in high winds. No wonder so many Long Islanders have purchased private generators for the blackouts to come.

In New York City, where more than half of local power plants are in the hundred-year flood plain, the storm surge from Sandy breached the walls at Con Ed’s East Village substation and caused a five-day blackout in downtown Manhattan. Today, thanks to higher protective barriers and elevated equipment at power stations, a recurrence on that scale is less likely—unless, of course, there’s a prolonged and severe heat wave, akin to the three-week disaster that hit Europe in 2003, and soaring demand proves impossible to meet.

Heat and wind, I learned, are what currently worry leaders of New York City’s medical system, who have spent the past three years protecting against water. During Sandy, the power outage and flooding forced several hospitals and other health-care facilities around the city to close. At New York University’s Langone Medical Center—where generators were served by underground and vaulted fuel oil tanks required by code to be on the lowest level of the building—floodwater cut off backup electricity and made basic caregiving impossible. Administrators report that roughly a thousand medical and professional staff evacuated three hundred and twenty-two patients, including twenty babies who had to be carried down nine floors from the neonatal intensive-care unit and pediatric intensive-care unit after the elevators flooded. Miraculously, there were no fatalities.

N.Y.U. had been planning to upgrade its medical facility before Sandy hit, and it received $1.4 billion for repairs from FEMA, plus more from its insurer, after the storm. How is the facility more resilient? According to Paul Schwabacher, Langone’s senior vice-president for facilities management, the backup power systems, MRI machines, and linear accelerators have all been moved from the basement, and a new co-generator will be online soon. Langone has also built barriers that can protect the hospital from Sandy-level flooding, “including a giant hydraulic gate on the F.D.R. service road that we can raise in minutes. In the future, the barriers will be even higher,” Schwabacher said.

But for now, Brad Gair, Langone’s vice-president of emergency management and enterprise resilience, added, “No one in New York City is really prepared for a major wind event, and we could be facing Category 3 or 4 hurricanes. The debris from broken windows, construction sites, and even cranes would be truly dangerous.” The same is true for extreme heat, which could mean no power at hospitals for days. At N.Y.U., Schwabacher said, “We’ve invested a lot in backup power systems for air-conditioning, so Langone should be O.K., but not all other hospitals. That’s a code requirement for hospitals in Florida, where they have tropical weather, but not in New York. With climate change, it probably should be here, too.”

Planning cities for climate change requires going far beyond updated building codes; it also involves what Klaus Jacob calls “pro-building” structures and infrastructures in anticipation of a warmer, wetter, and wilder world. In late 2012, President Obama’s Hurricane Sandy Rebuilding Task Force created the Rebuild By Design competition, to promote and develop innovative projects that enhance climate security while also improving the quality of everyday life. (I was the project’s research director, and served on the jury.) The task force selected ten finalists from the hundred and forty-eight initial submissions, and these ten teams did nine months of research and community engagement before submitting final proposals. In June, 2014, Shaun Donovan, the HUD secretary, announced that the federal government would award nine hundred and thirty million dollars to six winning projects in New York and New Jersey, most of which are advancing toward development.