NEW YORK -- NBC Universal and two partners said yesterday that they have reached a deal to buy The Weather Channel from Norfolk, Va.-based Landmark Communications Inc.

Financial terms weren't disclosed, but a person familiar with the matter who insisted on anonymity said the purchase price was $3.5 billion in cash. NBC was joined in the deal by the private equity firms The Blackstone Group LP and Bain Capital LLC.

In addition to The Weather Channel, which can be seen by 97 percent of U.S. cable subscribers, the deal also includes several related assets such as weather services for newspapers and radio stations and the widely used Web site Weather.com.

Weather.com drew 36.4 million U.S. viewers in May, according to Reston, Va.-based researcher ComScore Inc., making it the 15th most-popular Internet property. NBC sites, excluding iVillage.com, didn't rank in the top 50.

NBC, owned by General Electric Co., and Landmark said in a statement that The Weather Channel would be operated as a separate entity out of its base in Atlanta. They said they expected the transaction to close by year-end, pending regulatory approvals.

NBC became the sole bidder for The Weather Channel last month after Time Warner Inc. dropped out. CBS Corp. and cable industry leader Comcast Corp. also had expressed interest.

Started in 1982, The Weather Channel provides 24-hour programming. The network, with about 110 meteorologists among its 800 employees, started a high-definition channel in October.

Landmark, a privately held media company owned by the Batten family, put The Weather Channel up for sale in January along with its other businesses. Its daily newspapers include The Virginian-Pilot, The Roanoke Times in Virginia, The Capital in Annapolis, Md., and the News & Record in Greensboro, N.C. In addition, it owns Style Weekly in Richmond and CBS-affiliated TV stations in Las Vegas and Nashville, Tenn.

Landmark had $1.75 billion in sales in 2006 and 12,000 employees, according to Hoover's Inc. The company doesn't release earnings.