Australia’s Cloudy Beauty

Earth Observatory Science Earth Observatory Australia’s Cloudy Beauty Earth Earth Observatory Image of the Day EO Explorer Topics All Topics Atmosphere Land Heat & Radiation Life on Earth Human Dimensions Natural Events Oceans Remote Sensing Technology Snow & Ice Water More Content Collections Global Maps World of Change Articles Notes from the Field Blog Earth Matters Blog Blue Marble: Next Generation EO Kids Mission: Biomes About About Us Subscribe 🛜 RSS Contact Us Search Fog fills networks of river valleys in eastern Victoria in an image captured by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite at 8:19 a.m. local time (22:19 Universal Time) on May 11, 2026. NASA Earth Observatory / Lauren Dauphin It’s autumn in the Southern Hemisphere, which means it’s fog season in the Victorian Alps. NASA’s Terra satellite captured this view of morning fog filling valleys in several national parks across the mountains of eastern Victoria in May. As nights lengthen with the season, the atmosphere has more time to cool and approach the dew point—the temperature at which the air becomes saturated and water vapor can condense into radiation fog. Because cold air is denser than warm air, it sinks and drains into valleys, allowing fog to develop there first. In low-elevation areas, radiation fog usually fades as the Sun warms the ground, but it tends to linger in mountain valleys because they remain shaded longer. On this day, geostationary satellite imagery shows the fog persisting for about two hours. Fog is a low-lying type of cloud composed of tiny water droplets suspended in the air. The main difference between a cloud and fog is that the base of fog reaches the ground, while the base of a cloud is generally well above the surface. Radiation fog forms in clear, calm conditions at night. In this case, a blast of cold, soggy weather primed the region by moistening land surfaces a few days prior to the arrival of a slow-moving high t