Observe various severe weather phenomena in this image gallery from WGBH. Weather is the combination of factors -- temperature, wind, snow or rain, and sunlight and clouds -- that happen in a specific place at a specific time. Sometimes the combination of factors describes different types of threatening weather conditions that can be severe and dangerous, such as a powerful blizzard or windstorm. Students can use the images in the gallery to observe various severe weather conditions and compare factors across the conditions. A Background Essay, Student Activity, and Teaching Tips are provided.