The surge in New York—rising more than twofold in New York City and nearly doubling in Nassau and Westchester in the past decade—far exceeds more modest increases across the rest of the country, according to the Federal Emergency Management Agency, which backs most flood-insurance policies.
Nationally, the number of flood-insurance policies has risen 26.7%. In the middle of the past decade, New York experienced a series of storms and floods at the same time that devastating Gulf of Mexico hurricanes such as Katrina and Rita were dominating headlines, leading to more flood-insurance policies, insurance agents said.
"Katrina did a lot of it," said Rino Pietanza, who sells insurance at Summit Coverages Ltd. in Brooklyn. "In the last few years, there are more dramatic weather events that have been occurring."
Insurance agents said a widespread perception that the weather is becoming more extreme is part of what's driving the surge. Mr. Pietanza said his agency now heavily promotes flood insurance after storms, including the record rains that fell on the region earlier this month.
Those storms caused the city's sewer system to overload, flooding streets and basements in Staten Island and Queens with a mix of water and sewage.
Forecasters say it's not clear what effects climate change could have on New York and whether it would cause more floods. But big storms with heavy media coverage have an effect on perception, said Anthony Barnston, the chief forecaster at the International Research Institute for Climate andSociety at Columbia University.
"Single extreme events have played a psychological role," Mr. Barnston said.
The trend may continue this year, as meteorologists are also predicting a more active than normal Atlantic hurricane season, which runs through the end of November.
Residents who purchase or refinance homes located in FEMA-drawn maps of flood-prone areas are generally required by law to buy flood insurance.
Between 2007 and 2009, FEMA redrew the maps in and around New York, in many instances widening the area where insurance was required and helping to fuel the surge in policies.
The insurance premiums cost anywhere from a few hundred dollars a year for those not in flood-prone areas to more than $2,000 a year for waterfront property.
But agents said many more people with homes outside of federally designated flood areas are purchasing insurance, just to be safe. In 2010, there were 37,780 federally backed flood-insurance policies in New York City, up from 14,356 in 2001. In Nassau and Westchester, the number rose 88%, to 50,828.
Frank Rossi, a 64-year-old retiree, carries flood insurance, even though he lives on a high point in Huntington, Long Island, far from the Long Island Sound. His home hasn't been flooded in the 23 years he's owned the house.
He bought flood insurance anyway five years ago, just in case. His decision was motivated in large part by cost. Because he isn't in a flood zone, his premium is a few hundred dollars.
"You never know what's going to happen here," he said.
Banks have also played a role in the spike, insurance agents and homeowners say. Agents said they've noticed banks are asking more borrowers to purchase flood insurance when they buy a new home or refinance. Banks say they only require it of homeowners in federally designated flood zones.
Steve Siciliano, an Italian marble and tile salesman, said Wells Fargo told him to buy flood insurance when he bought a new home recently in Bay Ridge located about three blocks from the shore of New York Harbor.
He balked and successfully argued against buying the insurance. "I said, 'Wait a second, I'm in Brooklyn,'" Mr. Siciliano said. "I've never heard of flood damage in Brooklyn. Somehow I was able to convince them."
A spokesman for Wells Fargo said the company didn't have any record of conversations with Mr. Siciliano about flood insurance.
Mr. Siciliano said another bank asked him to purchase flood insurance when he refinanced his home in Sag Harbor. This time, he relented because his home there sits just feet from the water. The cost is $2,200 a year.
"I said, 'OK, I'm probably tempting fate,'" Mr. Siciliano said. "I'm 30 years closer to that 100-year storm, so when September rolls around I want to have a little peace of mind."