Weather Underground’s devotion to weather data has brought the site about 10 million unique visitors a month, according to the measurement firm ComScore, and has helped it to remain an independent company for the better part of two decades. A similar site, WeatherBug, draws 21 million visitors a month. (WeatherBug is owned by Earth Networks.)

Both sites, however, are dwarfed by Weather.com and the other properties owned by the Weather Channel, which is owned by a consortium that includes Comcast, Bain Capital and the Blackstone Group. The Weather Channel sites draw almost 50 million visitors a month. But only half of Weather Underground’s users also use Weather.com in a given month, which might be considered a silent protest of sorts.