Weather Underground is a commercial weather service, which provides real-time weather information via the Internet. Weather Underground provides weather reports for most major cities across the world on its website, as well as local weather reports for newspapers and websites. Most of its United States information comes from the National Weather Service (NWS), as federal law specifies that information from that agency falls within the public domain. The website is available in many languages, and customers can access an ad-free version of the site with additional features for an annual fee.