Abstract: Techniques for weather information extraction using image data are described herein. In accordance with the present disclosure, economical weather data collection devices may be installed in any places on the earth, and form a dense network of weather data collection devices. Preferably, these weather data collection devices include image capture components that may capture series of sequential images over time (i.e., image streams) from any particular locations. The disclosed techniques include extracting a sky portion from a series of time-sequenced images. The extracted sky portion may be used for determining cloud coverage, a sun track, and so on, thereby enabling to provide accurate weather forecast as well as other weather data mining abilities.