Jupiter’s temperatures span an extraordinary range, from about 110 kelvin (around −160 °C) near the visible cloud tops to an estimated 900 K in the wispy upper thermosphere and likely tens of thousands of degrees deep in the interior. That makes the planet both far colder and far hotter than most people expect, depending on where you measure. Because Jupiter has no solid surface, “how hot is Jupiter” is really a question about altitude and pressure, with every layer telling a different thermal story shaped by sunlight, internal heat, storms, and exotic chemistry.
A Scorching Upper Atmosphere
The thinnest, highest reaches of Jupiter’s atmosphere are, paradoxically, extremely hot. Data from the Galileo probe’s deceleration as it plunged into Jupiter in 1995 showed that temperatures climb from about 109 K at the 175-millibar pressure level to roughly 900 K at the 1-nanobar level, the near-vacuum fringe of the atmosphere.1PubMed. Thermal Structure of Jupiter’s Upper Atmosphere Derived from the Galileo Probe That is a jump of nearly 800 degrees over a stretch of atmosphere so thin it barely registers as having any gas at all.
The jump has puzzled planetary scientists for decades. The Sun is too far away and too faint at Jupiter’s distance to heat the thermosphere to 900 K through ultraviolet absorption alone. Auroral heating at the poles was an obvious candidate, but models struggled to explain how that energy could spread to lower latitudes without invoking some unknown braking force. Recent modeling work suggests the answer lies in Jupiter’s powerful magnetic field: ion drag from the field slows down high-altitude winds enough that heat from the auroral zones can redistribute globally, raising temperatures across the thermosphere without needing any artificial friction term in the models.2The Astrophysical Journal Letters. Temperatures of Jupiter’s Upper Atmosphere: The Role of the Planetary Magnetic Field The so-called “energy crisis” of Jupiter’s upper atmosphere may finally have a plausible solution.
Through the Cloud Decks
Drop below the thermosphere and temperatures plummet. Around the 1-bar pressure level, roughly equivalent to sea-level pressure on Earth, Jupiter’s atmosphere sits near 165 K (about −108 °C). This is the zone of ammonia ice clouds, the bright bands visible through backyard telescopes.
The Galileo probe provided the only direct in-situ measurements of what happens beneath those clouds. As it descended on its parachute, it recorded temperatures and pressures that followed a smooth, predictable lapse rate between about 0.4 and 24 bars, consistent with a well-mixed column of hydrogen and helium with no deep water cloud at that location. Between roughly 5 and 15 bars, the temperature gradient was slightly more stable than pure convective mixing would produce, hinting that simple up-and-down circulation wasn’t the only process transporting heat in that pressure range.3PubMed. Structure of the Atmosphere of Jupiter: Galileo Probe Measurements
By the time the probe reached 24 bars, about 150 km below the 1-bar cloud deck, temperatures had climbed to around 425 K (roughly 150 °C), hot enough to boil water at Earth’s surface pressure. And that was only a tiny fraction of the way toward Jupiter’s center.
What Juno Sees Below the Clouds
The Galileo probe sampled a single column of atmosphere before it was crushed. Juno’s microwave radiometer, orbiting overhead since 2016, provides a fundamentally different view: a global map of thermal emissions from the cloud tops down to pressures of about a hundred bars.4Geophysical Research Letters. The distribution of ammonia on Jupiter from a preliminary inversion of Juno microwave radiometer data
One of the surprises from Juno is that Jupiter’s familiar belt-and-zone banding doesn’t stay the same at depth. Near the cloud tops, the brownish belts are warmer in microwave observations and the whitish zones are cooler. But somewhere between about 4 and 10 bars, that contrast flips. Researchers call this transition level the “jovicline,” and it likely reflects a shift in where ammonia gas is concentrated and how temperatures are distributed at greater depths.5Journal of Geophysical Research: Planets. Jupiter’s Temperate Belt/Zone Contrasts Revealed at Depth by Juno Microwave Observations
Juno has also turned its radiometer toward Jupiter’s poles, which are nearly impossible to study from Earth. Observations from multiple polar passes reveal that the deep polar atmosphere is warmer than expected, with ammonia and water abundances at depth resembling equatorial values.6The Astrophysical Journal. Juno Microwave Radiometer Observations Reveal a Warmer Polar Atmosphere on Jupiter That finding complicates the old picture of Jupiter as a planet with a simple equator-to-pole temperature gradient and suggests deep mixing is more vigorous than models once assumed.
Storms That Rearrange the Heat
Jupiter’s storms do more than look dramatic. They actively reshape the planet’s thermal structure. The Great Red Spot, an anticyclonic vortex larger than Earth, is generally cold at the cloud-top level because its high-altitude clouds block thermal radiation escaping from below. But high-resolution infrared imaging has revealed an elliptical warm core nestled inside the vortex, spanning about 8° of longitude and 3° of latitude. The temperature contrast between this warm core and the coldest parts of the spot reaches 3 to 3.5 K in the 150 to 500 millibar pressure range.7Icarus. Thermal structure and composition of Jupiter’s Great Red Spot from high-resolution thermal imaging JWST’s mid-infrared instrument mapped the Great Red Spot in 2022 alongside coordinated observations from Hubble and ground-based telescopes, providing the most detailed thermal portrait of the vortex to date.8Journal of Geophysical Research: Planets. The Thermal Structure and Composition of Jupiter’s Great Red Spot From JWST/MIRI
Smaller, more violent convective storms leave an even more dramatic thermal footprint. Juno’s microwave radiometer observed a large storm that erupted in 2017 and found that it heated the upper atmosphere while simultaneously depositing ammonia and water well below the level where the storm originally formed.9PubMed Central. Tempests in the troposphere: Mapping the impact of giant storms on Jupiter’s deep atmosphere The mechanism involves what researchers have nicknamed “mushballs,” hailstones made of a slushy ammonia-water mixture that form high in the atmosphere during powerful thunderstorms. These mushballs grow in a process analogous to hailstone formation on Earth, then fall deep into the atmosphere and evaporate at pressures between roughly 5 and 27 bars. Because the ammonia sits in the mushball’s core, it gets delivered to even deeper levels than the water, effectively draining the upper atmosphere of ammonia and dumping it far below the expected cloud base.10Journal of Geophysical Research: Planets. Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of “Mushballs” This process helps explain one of Juno’s most puzzling early findings: ammonia concentrations that remain variable down to tens of bars, far deeper than any cloud condensation should reach.11Journal of Geophysical Research: Planets. Storms and the Depletion of Ammonia in Jupiter: II. Explaining the Juno Observations
Jupiter Radiates More Heat Than It Receives
A key to understanding why temperatures keep rising below the clouds is that Jupiter generates its own heat. The planet radiates substantially more energy into space than it absorbs from the Sun. Updated measurements put its Bond albedo, the fraction of sunlight reflected away, at about 0.50, meaning half of the incoming sunlight bounces straight back to space. The internal heat flux is estimated at roughly 7.5 watts per square meter, and the ratio of total emitted thermal power to absorbed solar power comes out to about 2.1.12Nature Communications. Less absorbed solar energy and more internal heat for Jupiter In plain terms, Jupiter puts out more than twice the energy it gets from the Sun.
Earlier estimates from the Voyager era had placed the internal heat flux lower, at about 5.4 watts per square meter with an energy balance ratio of roughly 1.67.13Journal of Geophysical Research: Space Physics. Albedo, internal heat, and energy balance of Jupiter: Preliminary results of the Voyager Infrared Investigation The nearly 40% upward revision matters because it changes how modelers think about the rate at which Jupiter is cooling and contracting, which in turn affects estimates of conditions deep inside the planet.
The primary source of this internal heat is the slow gravitational contraction left over from Jupiter’s formation about 4.5 billion years ago. The planet is still shrinking by a tiny amount, converting gravitational potential energy into thermal energy. An additional contribution comes from helium rain: at pressures around a million bars and temperatures of a few thousand kelvin, hydrogen and helium become partly immiscible. Helium-rich droplets form and sink toward the interior, releasing gravitational energy as they fall.14The Planetary Science Journal. Stable Stratification of the Helium Rain Layer Yields Vastly Different Interiors and Magnetic Fields for Jupiter and Saturn This process acts like a slow drip-feed of extra heat and also explains why Jupiter’s outer envelope is slightly depleted in helium compared to the ratio expected from the primordial solar nebula.
Metallic Hydrogen and the Fuzzy Core
Below the molecular atmosphere, pressures climb to millions of bars and temperatures reach roughly 10,000 K. At these conditions, hydrogen is squeezed so hard that it behaves like a liquid metal, conducting electricity and generating Jupiter’s enormous magnetic field. Standard interior models divide Jupiter into three broad layers: an outer envelope of molecular hydrogen and helium, an inner shell of metallic hydrogen, and a dense central core.15Journal of Geophysical Research: Planets. Understanding Jupiter’s interior
But Juno’s gravity measurements have complicated this neat picture. Rather than a compact ball of rock and ice at the center, Jupiter appears to have what researchers call a “fuzzy” or “dilute” core, a central region enriched with heavy elements but with no sharp boundary separating it from the surrounding metallic hydrogen.16AGU Advances. The Fuzzy Cores of Jupiter and Saturn One idea for how such a structure formed is that a giant impact early in Jupiter’s history disrupted a primordial compact core and mixed heavy elements outward. Simulations of such impacts, however, have so far struggled to reproduce a dilute core, leaving the origin question open.17Monthly Notices of the Royal Astronomical Society. No dilute core produced in simulations of giant impacts on to Jupiter
Estimates for the temperature at Jupiter’s very center vary depending on the model, but most fall in the range of roughly 20,000 to 40,000 K. That is hotter than the visible surface of the Sun, sustained not by nuclear fusion but by the immense pressure of the overlying mass. And because there is no discrete boundary between the “core” and the hydrogen above it, the temperature gradient in this region is smoother than you might expect: not a sudden jump from cool gas to blazing rock, but a steady climb over thousands of kilometers.
Temperatures That Shift Over Years and Decades
Jupiter’s temperatures are not static. Ground-based infrared monitoring spanning 40 years has uncovered rhythmic fluctuations in the upper troposphere at about 330 millibars. Several periodicities emerge, at roughly 4 years, 7 to 9 years, and 10 to 14 years, involving different latitude bands. These oscillations do not line up neatly with seasonal changes in sunlight, and opposite hemispheres sometimes swing in opposite directions at matching latitudes. Equatorial temperature variations at cloud-top level are anticorrelated with those observed 60 to 70 km higher up, as if the atmosphere is seesawing vertically.18Nature Astronomy. Unexpected long-term variability in Jupiter’s tropospheric temperatures
Higher in the stratosphere, Jupiter hosts its own version of oscillating equatorial wind patterns. Called the quasi-quadrennial oscillation because its period is closer to four years, it produces alternating layers of eastward and westward jets stacked vertically above the equator. Mapping of these winds has revealed a strong westward jet at about 4 millibars with speeds near 200 meters per second, and an eastward jet above it near 0.1 millibar, with a wind-speed difference of about 300 meters per second between the two layers.19Astronomy & Astrophysics. Mapping the zonal winds of Jupiter’s stratospheric equatorial oscillation These oscillating jets modulate wave activity at higher latitudes, with dominant wave patterns showing long-term amplitude changes that track the equatorial wind shifts.20Journal of Geophysical Research: Planets. Long‐Term Variations of Jupiter’s Stratospheric Planetary Waves Modulated by the Quasi‐Quadrennial Oscillation The upshot is that a temperature map of Jupiter taken today may look noticeably different from one taken two or three years from now, even without any visible storm activity.
When Comets Strike
External events can jolt Jupiter’s thermal profile, too. When Comet Shoemaker-Levy 9 broke apart and slammed into Jupiter over six days in July 1994, the fragments punched into the atmosphere and released enormous amounts of energy. Infrared observations from NASA’s telescope on Mauna Kea showed that every impact warmed the stratosphere and some heated the troposphere by several degrees.21PubMed. Collision of comet Shoemaker-Levy 9 with Jupiter observed by the NASA infrared telescope facility The chemical and thermal disturbances at the impact sites persisted for periods ranging from minutes to weeks, altering both temperature and atmospheric composition over regions visible even through modest telescopes.22PubMed. Chemical and thermal response of Jupiter’s atmosphere following the impact of comet Shoemaker-Levy 9
Those impacts served as an unplanned experiment, revealing how Jupiter’s atmosphere responds to sudden energy injections and offering constraints on how quickly the stratosphere relaxes back to normal. The 1994 event remains the only observed collision between a comet and a planet, but Jupiter’s strong gravity makes it a frequent target for smaller, unobserved impacts that likely produce localized heating on a regular basis.
Why Getting Jupiter’s Heat Right Matters for Distant Worlds
Getting Jupiter’s internal thermal profile right has consequences well beyond our own solar system. Interior models that account for non-convective layers, like the stable helium rain zone, predict different cooling rates and radii for a given planetary mass and age than models assuming free convection throughout.23The Astrophysical Journal. The Evolution and Internal Structure of Jupiter and Saturn with Compositional Gradients Since astronomers routinely estimate the masses and compositions of giant exoplanets by comparing observed radii to model predictions, Jupiter acts as a calibration point. A planet that cools more slowly because of internal stratification will look larger at a given age than one that convects freely, and confusing the two scenarios could lead to wrong conclusions about what a distant world is made of.
Ground-based observatories continue to monitor Jupiter’s thermal emissions at mid-infrared wavelengths, building pole-to-pole maps of tropospheric and stratospheric temperature, aerosol distribution, and chemical composition that serve as a baseline for comparison with other giant planets.24Journal of Geophysical Research: Planets. Investigating Thermal Contrasts Between Jupiter’s Belts, Zones, and Polar Vortices With VLT/VISIR Jupiter is, in a real sense, the nearest laboratory we have for understanding hydrogen-dominated atmospheres: metallic hydrogen under millions of bars, helium phase separation at planetary scale, ammonia-water hailstorms falling through a sky that has no ground. Every layer of its temperature profile, from the frozen cloud tops to the searingly hot deep interior, encodes physics that shapes worlds across the galaxy.