Looks like they are using airport data (identified by ICAO ID) and ham radio data (probably via APRS, identified by callsigns), like this one: KA0RUX http://op

Looks like they are using airport data (identified by ICAO ID) and ham radio data (probably via APRS, identified by callsigns), like this one: KA0RUX http://openweathermap.org/station/10400 http://openweathermap.org/station/10400 http://www.findu.com/cgi-bin/wxpage.cgi?call=KA0RUX http://www.findu.com/cgi-bin/wxpage.cgi?call=KA0RUX There is also an API to feed new data if you have a weather station: http://openweathermap.org/stations http://openweathermap.org/stations