Cloud temperatures range from mildly cool to staggeringly cold, spanning roughly from just above freezing near the ground all the way down to about −111°C in extreme cases. The exact temperature inside any given cloud depends overwhelmingly on its altitude and how it formed. A low-hanging fog bank on a winter morning might sit right around 0°C, while a towering thunderstorm punching into the upper atmosphere can push its cloud tops into territory colder than anything found naturally at Earth’s surface.
Low and Mid-Level Clouds
The clouds most people see on a typical day, the puffy cumulus and flat stratus decks floating a kilometer or two above the ground, are not particularly cold. Their internal temperatures closely track the surrounding air, which cools at a fairly predictable rate as you climb. In the lower troposphere, air temperature drops roughly 6 to 7°C for every kilometer of altitude gained, though moisture and local conditions shift that number around. A cumulus cloud with its base at about 2,000 meters on a mild day might have an internal temperature near 2 to 5°C, chilly but well above freezing.
Mid-level clouds, the altocumulus and altostratus types that form between roughly 2,000 and 6,000 meters, tend to sit in the range of about 0°C down to −20°C or so. This is where things start to get interesting from a physics standpoint, because this temperature band is where water droplets and ice crystals can coexist. At these temperatures, a cloud is not necessarily frozen solid. Liquid droplets persist stubbornly even well below 0°C, a phenomenon that plays a major role in how precipitation forms.
Supercooled Water and the Freezing Puzzle
One of the more counterintuitive facts about clouds is that water inside them routinely stays liquid at temperatures far below the freezing point you learned about in school. Tiny cloud droplets, lacking the impurities and surfaces that normally trigger ice crystal growth, can remain liquid down to about −36 to −40°C. Below that threshold, ice formation becomes essentially unavoidable because the water molecules spontaneously rearrange into crystals at the droplet surface.
Research into this process has shown that surface crystallization of supercooled droplets helps explain why very little liquid water is observed in clouds near −40°C.1PubMed Central. Surface crystallization of supercooled water in clouds Above that temperature, though, clouds frequently contain a mixture of liquid and ice. The transition from all-liquid to all-ice does not happen at a single neat threshold. It depends on what particles are floating in the air to serve as seeds for ice formation. Field observations collected across many locations over more than a decade have demonstrated that ice first appears in clouds warmer than −36°C when suitable particles, known as ice nuclei, are present, and the concentration of those nuclei depends heavily on temperature and the number of larger particles in the air.2PubMed Central. Predicting global atmospheric ice nuclei distributions and their impacts on climate
This mixed-phase zone, where ice and liquid water share space in the same cloud, matters enormously for weather. When ice crystals and liquid droplets sit side by side at the same temperature, the ice grows at the expense of the liquid. Water vapor pressure over ice is lower than over liquid water, so vapor migrates from the droplets to the ice crystals, causing the droplets to shrink and the ice to grow. This process, sometimes called the Wegener-Bergeron-Findeisen mechanism, is one of the main engines driving rain and snow production in mid-latitude storms.3Quarterly Journal of the Royal Meteorological Society. Rates of phase transformations in mixed‐phase clouds Climate models still struggle to represent it accurately because the mixing of liquid and ice within real clouds is patchy and uneven rather than smooth and uniform.4Geophysical Research Letters. Parameterizing the Heterogeneous Liquid‐Ice Mixing in Modeling Ice Growth Through the Wegener‐Bergeron‐Findeisen Process in CAM6
Cirrus and the Upper Troposphere
The wispy, high-altitude clouds known as cirrus are among the coldest features in the everyday sky. Cirrus clouds typically form in the upper troposphere at temperatures below −40°C and are composed entirely of ice crystals. Satellite observations of thin cirrus characterized by hollow ice crystals place their temperatures between about −60 and −40°C.5Geophysical Research Letters. The First Global Insight of Cirrus Clouds Characterized by Hollow Ice Crystals From Space‐Borne Lidar In-situ sampling by research aircraft has collected ice crystals from cirrus over mountain ranges at temperatures near −55°C and from deep tropical convection at around −48°C.6Cirrus. Ice Crystals in Cirrus
The crystals found at these temperatures come in a surprising variety of shapes: hexagonal plates, needles, columns, triangular forms, and irregular chunks, depending on the exact temperature and how much water vapor is available. The shape matters because it affects how the cloud scatters and absorbs sunlight. Despite looking delicate and nearly transparent from the ground, cirrus clouds exert a significant influence on Earth’s energy balance. They let most sunlight pass through but trap outgoing heat, which is one reason atmospheric scientists are keenly interested in understanding how they form and evolve.
The Coldest Cloud Temperatures on Record
The most extreme cloud temperatures on Earth come from the tops of massive tropical thunderstorms. When intense convection punches a tower of air through the tropopause and into the lower stratosphere, the overshooting cloud tops can reach temperatures far below anything in the surrounding atmosphere. In December 2018, a cluster of storm overshoots over the tropical western Pacific produced what is believed to be the coldest cloud-top temperature ever recorded by satellite: roughly −111°C (about 162 Kelvin).7Geophysical Research Letters. Record‐Low Cloud Temperatures Associated With a Tropical Deep Convective Event
To put that in perspective, −111°C is colder than the surface of Mars on a winter night and colder than any temperature recorded at ground level anywhere on Earth. These extreme cloud-top temperatures are transient, lasting perhaps minutes as the storm overshoots and then collapses, but they illustrate just how wide the temperature range of clouds really is. From a fog bank sitting at a few degrees below freezing to the top of a tropical supercell at −111°C, the spread covers well over 100 degrees Celsius.
When Clouds Sit on the Ground
Fog is essentially a cloud that forms at or very near the surface, and it can get quite cold. Cold fog, defined as fog forming at temperatures below 0°C, is a regular occurrence in mountainous terrain during winter. It can contain liquid droplets, ice crystals, or a mixture of both, depending on exactly how far below freezing the temperature dips.8Quarterly Journal of the Royal Meteorological Society. Evaluation of near‐surface and boundary‐layer meteorological conditions that support cold‐fog formation using Cold Fog Amongst Complex Terrain field campaign observations In sheltered mountain valleys where cold air pools overnight, temperatures during fog events can drop to −10 or −20°C, and the fog becomes a hazard for both drivers and pilots because the ice crystals coat surfaces rapidly.
Cold fog is also notoriously difficult to forecast. The conditions that produce it, very stable air trapped in a valley with just enough moisture, are sensitive to tiny local details like terrain shape and overnight radiation cooling. For anyone living in high-altitude valleys, the practical takeaway is that a fog event in winter is not just a visibility problem but often an icing problem too, because the cloud touching the ground contains supercooled droplets ready to freeze on contact with any solid surface.
Contrails and Human-Made Clouds
Jet aircraft create their own clouds, and the temperature requirements for those contrails tell you something about just how cold the upper troposphere is. Contrails form when hot, humid exhaust from jet engines mixes with the extremely cold ambient air and the mixture temporarily reaches saturation. Observations during research flight campaigns have found that contrails persisted for more than a few minutes only when the surrounding air was substantially supersaturated with respect to ice over broad areas. On some occasions, contrails formed at temperatures as high as −50°C when the surrounding humidity was extremely elevated.9Journal of Geophysical Research: Atmospheres. Environmental conditions required for contrail formation and persistence
At temperatures above about −50°C, contrails can only form if the air is already supersaturated with respect to ice, which means any contrail that does form in those conditions will likely persist and spread. This is why on some days you see long-lasting contrail lines spreading into sheets of artificial cirrus, while on other days the white trails behind a jet vanish within seconds. The difference is not the aircraft or the altitude alone; it is the temperature and humidity of the air the plane flies through. Persistent contrails contribute to aviation’s climate impact because they act like thin cirrus, trapping outgoing heat.
Clouds Above the Troposphere
Most weather-related clouds live in the troposphere, the lowest layer of the atmosphere, which tops out at roughly 8 to 17 kilometers depending on latitude and season. But clouds also form much higher, and those clouds are colder still.
Polar stratospheric clouds form in the stratosphere at altitudes around 15 to 25 kilometers, primarily during winter over the polar regions. They require temperatures below about −78°C for the nitric acid and water vapor types, and below roughly −85°C for the pure ice variety. These clouds play a central role in the chemical destruction of ozone, because their surfaces host reactions that convert stable chlorine-containing molecules into forms that destroy ozone once sunlight returns in spring.10Reviews of Geophysics. Polar Stratospheric Clouds: Satellite Observations, Processes, and Role in Ozone Depletion They also remove key chemical species from the gas phase by locking them into particles that fall to lower altitudes, prolonging the conditions that allow ozone destruction to continue.
Higher still, near the edge of space at roughly 80 to 85 kilometers altitude, noctilucent clouds form in the mesosphere during summer at high latitudes. The summer mesopause is the coldest part of Earth’s atmosphere, reaching temperatures near −130°C or below. This is cold enough to freeze the trace amounts of water vapor present at those extreme altitudes into tiny ice crystals despite the air being extraordinarily dry.11Journal of Geophysical Research: Atmospheres. Dynamics, radiation, and photochemistry in the mesosphere: Implications for the formation of noctilucent clouds These clouds are visible only around twilight, when the sun has set at ground level but still illuminates the mesosphere, giving them an eerie electric-blue glow. They represent some of the coldest cloud environments anywhere on the planet, with temperatures that dwarf even the record-setting tropical thunderstorm tops.
How Scientists Measure Cloud Temperatures
Measuring the temperature inside a cloud sounds straightforward, but it comes with real complications. The most direct method is to fly an instrumented aircraft through the cloud. Modern research planes carry temperature sensors shielded to protect their sensitive elements from the impact of cloud droplets, which can throw off readings by evaporating on contact and cooling the sensor. These instruments typically achieve an accuracy of about 0.3 to 0.4°C, which is good enough for most research purposes but still leaves room for error when conditions are turbulent or the liquid water content is high.12Atmospheric Research. A method to determine true air temperature fluctuations in clouds with liquid water fraction and estimate water droplet effect on the calculations of the spectral structure of turbulent heat fluxes in cumulus clouds based on aircraft data
For cloud tops that are too high or too dangerous for aircraft, satellites step in. Infrared sensors on satellites can estimate cloud-top temperatures by measuring the thermal radiation the cloud emits. Colder surfaces emit less radiation, so a very cold reading corresponds to a very high, very cold cloud top. The challenge is that the satellite “sees” the temperature at the effective radiating level of the cloud, which may not be the exact physical top. For optically thick ice clouds, satellite-based estimates of the cloud’s effective radiating height can differ from the true physical top by about 1.6 kilometers on average, a gap that can be corrected using lidar measurements from instruments that bounce laser pulses off the cloud and measure altitude directly.13Geophysical Research Letters. Estimating the top altitude of optically thick ice clouds from thermal infrared satellite observations using CALIPSO data
Radiosondes, the instrument packages carried aloft by weather balloons, provide another source of temperature data through the atmosphere and can profile conditions in and around clouds. Combining all these methods gives scientists a layered picture. Aircraft give direct, precise measurements inside the cloud. Satellites give global coverage of cloud-top temperatures. Balloons fill in the vertical temperature profile. None of these methods is perfect alone, but together they produce a consistent picture of how cold clouds get at every altitude.
Clouds Beyond Earth
Earth is not the only planet with clouds, and the temperature ranges on other worlds make our atmosphere look almost temperate by comparison. Venus has thick clouds of sulfuric acid droplets at temperatures around −40 to −70°C in its upper atmosphere, though the surface below bakes at over 450°C. Jupiter and Saturn host clouds of ammonia ice, ammonium hydrosulfide, and water at various depths, with temperatures ranging from about −150°C in the visible ammonia cloud deck to much warmer conditions deeper down. Neptune’s atmosphere, among the coldest in the solar system, has methane ice clouds at temperatures near −200°C.
Exoplanet research has expanded the concept of clouds even further. Theoretical models and some observational evidence suggest that planets orbiting close to their host stars can have clouds made of substances that would be unrecognizable as cloud material on Earth, including vaporized rock, molten glass, and metallic compounds like iron. The temperatures in those cloud layers can exceed 1,000°C, putting them at the opposite extreme from the frozen wisps of our own cirrus or the frigid ice crystals in noctilucent clouds. Earth’s cloud temperature range, while broad by everyday standards, occupies a fairly narrow slice of what the universe apparently considers normal for atmospheric condensation.