NBC Universal and private equity heavyweights Bain Capital and Blackstone Group have sealed the deal to acquire the Weather Channel from Landmark Communications.

Financial terms were not disclosed, but it’s understood that the purchase price wound up at just under $3.5 billion.

Details of the ownership structure among NBC U, Bain and Blackstone were also not immediately disclosed, though NBC Universal will have managing control of the asset, NBC U prexy Jeff Zucker told Daily Variety on Sunday.

Purchase includes the mothership channel, available in 96 million cable and satellite TV homes; the website Weather.com, which brings in 40 million unique visitors per month; and the worldwide forecasting operation Weather Services Intl.

Weather Channel also owns 50% of Canada’s Pelmorex, which operates the dominant Canuck weather forecasting services, Weather Network and Meteo Media.

Based in Atlanta, the Weather Channel will be run as a separate entity from the Peacock’s other cable holdings because of the ownership structure, but will be managed by NBC U brass. Deal is expected to close by year’s end.

“You will see the Weather Channel becoming as much a part of NBC Universal as all of our other (TV) properties, and you will see all the other NBC Universal properties on the Weather Channel,” Zucker said.

Weather Channel, one of cable TV’s few sizable indie outlets, was formally put up for sale by its Norfolk, Va.-based parent company in January. Landmark initially sought $5 billion for the widely distribbed channel, but economic woes and limited interest from larger media concerns put a damper on the bidding process.

Time Warner was said to be the only other serious contender for the channel, and it withdrew its offer last month.

NBC U pursued the acquisition as a bid to further strengthen the Peacock’s portfolio of news and information-based assets, and the Weather Channel has the added perk of coming with a highly successful website and mobile-based biz. Weather Channel was a pioneering cable programming service, bowing on-air in 1982. Website Weather.com site launched in 1995.

“When you look at how strong we are with NBC News, CNBC, MSNBC, and now you add the Weather Channel to that — it really gives us a suite of unparalleled assets, and it gives us a real push ahead in digital,” Zucker said. “This is where we see the strength of our company in the coming years — cable and digital, and this deal is part of our strategy of continuing to make cable the backbone of NBC Universal.”

Bain Capital managing director Ian Loring said the partners were bullish on the “growth potential” of Weather Channel’s various businesses. Blackstone senior managing director Michael Chae called the company “a premier media asset with a unique position across all three screens: television, PC and mobile.”

Acquisition of Weather Channel probably spells the end for NBC’s nearly 4-year-old NBC Weather Plus, a digital cable channel and website jointly run between the Peacock and about 90 of its NBC broadcast network affiliate stations. Service bowed in 2004, but has had trouble gaining traction as a digital channel with cable operators. Zucker said a formal decision about the fate of Weather Plus would be made in the near future.