The recent weeks of tropical storms and other wet weather have pushed a new wave of homeowners into the market for flood insurance. What they are finding, however, are policies better suited to Tampa, Fla., than Teaneck, N.J.

Insurance companies have reported a surge of demand for flood insurance in the wake of storms Irene and Lee, even in landlocked states like Pennsylvania and Vermont, which both suffered flooding in some areas. Chubb Corp. says inquiries about and applications for its flood policies are up about 30% since late August, compared with the same period a year ago. Farmers Insurance Group of Cos. says its sales of federal flood insurance rose as much as 38% from July to August in some Northeastern states, and some independent insurance agents in the Northeast say that since Hurricane Irene in particular, up to 10% of clients have inquired about or applied for flood insurance.

But basic flood policies, most commonly provided by the National Flood Insurance Program and sold through private companies, cover damage starting on a home's first, above-ground floor, with limited coverage for basements. That usually is adequate in the Gulf Coast region, where houses don't tend to have below-ground levels. But it is less so in the rest of the country, where those features are common, says John Prible, vice president for federal government affairs at the Independent Insurance Agents and Brokers of America, an industry group. Federal flood policies will pay to replace specific items in a flooded basement, including hot water heaters, furnaces or other mechanical equipment, but ruined carpeting, furniture and fixtures would be excluded.

For many homeowners in the Northeast, the limits of coverage may not be enough. The federal flood program will cover up to $250,000 to rebuild a home and $100,000 in contents. That may suffice in New Orleans, says Scott Simmonds, an insurance consultant in Saco, Maine, but it falls short in Boston or New York, where materials and labor costs are higher.

To have full coverage, then, homeowners in the Northeast could need at least three different insurance policies, Mr. Prible says: basic home insurance; additional flood insurance; and a third, supplemental flood policy that would cover damage to basements and cellars, and also offer higher limits.

The costs quickly add up. While they vary widely, homeowners insurance premiums averaged about $800 a year in 2010; flood insurance adds another $600 on average. Premiums for supplemental flood coverage vary widely depending on the area of the house, but in states where the risk of floods is deemed low, additional flood coverage could add another $300 to $400 for a $500,000 home with a basement, according to Fireman's Fund Insurance Co., a subsidiary of Allianz SE.

As pricey as the coverage can be, and as rare as storms are, few homeowners hold on to flood insurance for long. Typically, demand spikes after extensive flooding, but homeowners usually let policies lapse within two to four years, according to a recent study by the Wharton Center for Risk Management and Decision Processes.