|Headquarters||San Francisco, California, United States|
|Parent||The Weather Company|
Weather Underground is a commercial weather service providing 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. Its information comes from the National Weather Service (NWS), and over 250,000 personal weather stations (PWS). 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. Weather Underground is owned by The Weather Company, a subsidiary of IBM.
The company is based in San Francisco, California and was founded in 1995 as an offshoot of the University of Michigan's Internet weather database. The name is a reference to the 1960s militant radical student group the Weather Underground, which also originated at the University of Michigan.
Jeff Masters, a doctoral candidate in meteorology at the University of Michigan working under the direction of Professor Perry Samson, wrote a menu-based Telnet interface in 1991 that displayed real-time weather information around the world. In 1993, they recruited Alan Steremberg and initiated a project to bring Internet weather into K-12 classrooms. WU's president Alan Steremberg wrote "Blue Skies" for the project, a graphical Mac gopher client, which won several awards. When the Mosaic Web browser appeared, this provided a natural transition from "Blue Skies" to the Web.
In 1995 Weather Underground, Inc. became a commercial entity separate from the university. It has grown to provide weather for print sources, in addition to its online presence. In 2005, Weather Underground became the weather provider for the Associated Press; WU also provides weather reports for some newspapers (including the San Francisco Chronicle) and the Google search engine. Alan Steremberg, Weather Underground's president, also worked on the early development of Google's search engine with Larry Page and Sergey Brin.
In October 2008, Jeff Masters reported that the site was #2 in Internet Weather for 2008.
In February 2010, Weather Underground launched FullScreenWeather.com, a full screen weather Web tool with integrated mapping and mobile device use in mind.
On July 2, 2012, The Weather Channel announced that it would acquire Weather Underground, which would become operated as part of The Weather Channel Companies, LLC, which was later renamed "The Weather Company". The Weather Underground website continues to operate as a separate entity from The Weather Channel's primary site, weather.com, with its existing staff retained. Third-party web analytics providers Alexa and SimilarWeb rate the site as the 117th and 98th most visited website in the United States respectively, as of July 2015. SimilarWeb rates the site as the second most visited weather website globally, attracting more than 47 million visitors per month. The Weather Company also uses the site's San Francisco headquarters as a regional office.
The website's popularity also helped launch a TV show hosted by meteorologist Mike Bettes, which airs on The Weather Channel from 6-8pm ET (except during storm coverage; in which case the show is extended to 9pm or 10pm).
On October 28, 2015, Jeff Masters noted that IBM had officially announced an agreement to acquire The Weather Company's business-to-business, mobile and cloud-based web properties, including Weather Underground, WSI, weather.com, and also the Weather Company brand. Meanwhile, the television service (The Weather Channel) remains a separate entity. The deal was finalized on January 29, 2016.
Web logs (blogs) are one of the main features in Weather Underground, allowing users of the site to create blogs about weather, everyday life and anything else. Jeff Masters started the first blog on April 14, 2005, and he now posts blog entries nearly every day. Richard B. Rood has been writing blogs on climate change and societal response since 2007, with new entries on a weekly basis.
On October 14, 2016, the Wunderblog announced that it would be changing their name to Category 6, a name which was suggested by Jeff Masters. They decided on the name because it "alludes to our deep fascination with all types of weather and climate extremes, including the many important facets of our changing climate", and "will provide all the insight and expert analysis needed to put the extreme events of our evolving 21st-century climate into context."
On April 3rd, 2017 Weather underground ended all Member blogs, WUMail, SMS alerts, NOAA Weather Radio rebroadcast and Aviation. As part of this transition, Category 6 will get a new look. All posts by Jeff Masters, Bob Henson and WU featured bloggers will move to Category 6. Users can no longer contact each other or have blogs.
Weather Underground also uses observations from members with automated personal weather stations (PWS). Weather Underground currently uses observations from over 250,000 personal weather stations worldwide.
The Weather Underground's WunderMap overlays weather data from personal weather stations and official NWS stations on a Google Map base and provides many interactive and dynamically updated weather and environmental layers. On December 15th, 2017, it was announced that user-provided weather cameras around the world would cease to be available. However, on December 7th, 2017 Weather Underground announced that they were reversing their position and would not be discontinuing the product based on significant user feedback. 
Weather Underground has several Google Chrome extensions and applications for iPhone, iPad and Android including FullScreenWeather.com, a redirect to a full screen weather viewer tied into OpenStreetMap. There is also an app developed for Roku devices.
In February 2015, Weather Underground released an iOS app called Storm. This app is universal, and can be used on both iPhone and iPad. Other apps by Weather Underground include WunderStation for iPad and WunderMap for iOS and Android. In 2017, Weather Underground removed support for "Storm," in favor of the "Storm Radar" app released by The Weather Channel Interactive in June 2017.|