OpenWeatherMap is online service that provides free API to weather data including current weather data, forecasts and history data to the developers of web-services and mobile applications. As a data source it uses official meteorological broadcast services, raw data from airports weather stations, raw data from radars, and raw data from official weather stations. All data are processed by unique mathematical algorithms that can provide accurate online weather forecast data flow and different weather maps like clouds and precipitations. On above of that the service is focused on social aspect by involving owners of weather stations to connect them to the service to increase accuracy of weather data. Ideology is inspired by OpenStreetMap and Wikipedia that make information free and available for everybody. It uses OpenStreetMap for display of weather maps. Every 10 minutes 10,000,000 people connect to the service and use weather data.