The appearance of green clouds during a thunderstorm is an unusual and striking sight. This distinct coloration results from a specific combination of atmospheric and optical conditions. Understanding this phenomenon explains why certain storms take on such an unexpected hue.
The Science Behind Green Clouds
The green color in thunderstorm clouds is primarily a result of how sunlight interacts with a storm’s unique composition. Sunlight contains all colors of the visible spectrum, and these colors behave differently when they encounter atmospheric particles. Water and ice particles within deep storm clouds can scatter blue light effectively. When reddish or yellowish light from a low sun, typically during sunrise or sunset, illuminates these blue-scattering water and ice droplets, the combination appears green to the human eye. This optical effect is similar to mixing blue and yellow paint to create green.
A significant amount of water content within the cloud is necessary for this color to manifest. Thunderstorms, especially those with substantial depth and water content, contain vast quantities of water and ice particles. These large droplets or ice crystals are crucial because they absorb red light, allowing the remaining blue and green wavelengths to dominate. A very deep and dense cloud is required for this particular light interaction to occur, filtering light in a way that allows green wavelengths to become visible.
Green Clouds and Severe Weather
Green clouds are often associated with severe weather, primarily large hail. The large water droplets and ice particles that contribute to the green hue are frequently hailstones. Strong updrafts within severe thunderstorms carry raindrops high into the atmosphere, where they freeze and grow into hailstones by colliding with supercooled water. The more hail and rain present in a storm cloud, the more likely the sky is to appear green.
Green clouds are almost exclusively seen with supercells, very strong, deep thunderstorms characterized by rotating updrafts. While green skies indicate heavy rain and hail, they do not guarantee a tornado. However, these intense storms can also generate damaging winds, heavy rainfall, and even tornadoes.
What to Do When You See Green Clouds
Observing green clouds is a visual cue that severe weather is approaching and requires immediate attention. Seek shelter without delay, as these clouds signal hazardous conditions such as large hail, strong winds, and intense lightning. Green skies indicate a powerful storm is in your vicinity.
Monitor local weather alerts and official warnings. Avoid being outdoors during these conditions, as hail and strong winds can cause significant harm. Do not attempt to get a closer look or take photos from an exposed position, as this puts you at risk. Prioritize safety and move to a secure location.