The Weather Channel deal is finally done, and announced on a lazy, bright and clear July 4th weekend Sunday: Landmark Communications has agreed to sell The Weather Channel to a consortium of NBC Universal (NYSE: GE) and two private equity firms, Bain Capital and The Blackstone Group. TWC will be operated as a separate entity, based in Atlanta as before, with management services to be provided by NBCU.

Financial terms of the transaction were not disclosed officially, but previous reports have pegged the deal in the $3.5 billion range, below the $5 billion Landmark hoped for when it started the sale process. NBCU, Blackstone and Bain would divide $1.8 billion of equity roughly equally in their bid…Blackstone’s GSO Capital—a hedge fund firm specializing in leveraged debt—would provide about $600 million in debt.

The transaction is expected to be completed by year-end, and is subject to receipt of customary regulatory approvals. With this deal, NBCU now controls Weather.com and its mobile channel, and of course the ubiquitous cable channel, making it the biggest weather-related multi-platform distribution outlet by far. NBC also has a much smaller weather operation, the 4-year-old Weather Plus, which includes a cable channel, often only available on digital cable platforms and found high on the dial, and the Weatherplus.com website…looks like these won’t be merged with TWC, though not sure if WeatherPlus will continue to exist.

TWC accounted for about one-quarter of Landmark’s 2007 revenues, which exceeded $2 billion, reports Virginian-Pilot. The weather businesses are expected to yield $550 million in revenues this year, it says.

Weather.com, launched in April 1995, gets about 37 million unique visitors every month, placing it among the 15 most heavily trafficked sites online…with this deal NBCU and its affiliated websites have a total unduplicated reach of nearly 70 million visitors per month, ranking No. 7 against all U.S.-based Internet properties, according to Comscore (NSDQ: SCOR) data for May 2008.

Deutsche Bank Securities acted as the lead investment bank for the consortium with Allen & Co. and Credit Suisse also providing financial advice. JPMorgan acted as Landmark’s bank. Deutsche Bank Securities, GE Commercial Finance, GSO Capital Partners and Sankaty Advisors will provide the debt financing for the transaction.