Weather Channel Acquiring Weather Underground

The Weather Channel Companies is going to gobble up one of its top competitors, the Weather Underground.

The acquisition, announced on Monday afternoon, will give the Weather Channel — already by far the most-visited weather news Web site in the United States — an even greater lead over other such companies. The deal is expected to be completed within weeks.

The purchase price was not disclosed, indicating that it is not material to the operations of the Weather Channel, which is owned by a consortium that includes Comcast, Bain Capital and the Blackstone Group. The owners have sought to reinforce Weather.com’s meteorological roots at the same time that they reposition the Weather Channel on television as a place for weather-based reality shows and documentaries.

In an interview, David Kenny,  the chairman and chief executive of the Weather Channel Companies, praised the Weather Underground site for having a “hard-core audience” of passionate weather fans. Some of them, he admitted, have sour views of the Weather Channel, which they see as overly corporate and dependent on advertising.

Acknowledging those concerns, Mr. Kenny said that the Weather Underground site, Wunderground.com, would continue to exist on its own. The unique weather data collected by the Weather Underground would be harnessed to improve the Weather Channel’s forecasts, he added.

“Weather Underground users can expect to see more of the same,” said Alan Steremberg, Weather Underground’s president. “But we’ll have a lot more resources to do fun things.”

Proudly independent for the better part of two decades, Weather Underground has about 10 million unique visitors a month, according to the measurement firm comScore. Weather.com and the other sites owned by the Weather Channel have almost 50 million visitors a month.

Only one other similar site is bigger than Weather Underground, and that’s WeatherBug, owned by Earth Networks, with 21 million visitors a month.