Surface temperatures on the Moon swing from scorching highs around 120°C (about 250°F) at the equator during the day to brutal lows around −178°C (about −288°F) just before sunrise. That roughly 300°C range dwarfs anything experienced on Earth, and it plays out over a single lunar day-night cycle lasting about 29.5 Earth days. But those headline numbers only tell part of the story, because where you stand on the Moon and what the ground is made of matter enormously.
How Hot the Daytime Surface Gets
At the lunar equator, peak daytime surface temperatures reach roughly 387 to 397 K, which works out to about 114–124°C (237–255°F). The exact peak depends on the reflectivity of the ground beneath your feet: darker surfaces absorb more sunlight and get hotter, while brighter patches reflect a bit more energy and stay slightly cooler.1Icarus. The global surface temperatures of the Moon as measured by the Diviner Lunar Radiometer Experiment Those numbers come from the Diviner Lunar Radiometer, an instrument aboard NASA’s Lunar Reconnaissance Orbiter that has mapped surface temperatures globally with high precision since 2009.2Journal of Geophysical Research: Planets. Lunar equatorial surface temperatures and regolith properties from the Diviner Lunar Radiometer Experiment
Several factors conspire to push daytime temperatures that high. The Moon has no appreciable atmosphere to scatter or absorb incoming sunlight before it reaches the ground. Its surface layer, called regolith, is a highly insulating blanket of fine, impact-pulverized dust. And the Moon rotates slowly enough that any given patch of equatorial ground sits under direct sunlight for about two straight weeks. Together, these conditions allow surface temperatures to nearly reach thermal equilibrium with the incoming solar energy, meaning the ground absorbs almost as much heat as the Sun can deliver before the long afternoon even begins to wane.1Icarus. The global surface temperatures of the Moon as measured by the Diviner Lunar Radiometer Experiment
How Cold It Gets at Night
Once the Sun sets on a given spot, that same insulating regolith works against you. The loose, powdery surface conducts heat poorly from below, so stored thermal energy barely trickles up to keep the surface warm. With no atmosphere to trap radiated heat the way Earth’s blanket of air does, the ground radiates its energy straight into space. Temperatures plummet steadily through the two-week-long night, bottoming out at roughly 95 K (about −178°C or −289°F) at the equator just before dawn.1Icarus. The global surface temperatures of the Moon as measured by the Diviner Lunar Radiometer Experiment
This nighttime cooling is strikingly uniform. Diviner measurements show that nighttime temperatures are remarkably similar across different longitudes and major geologic units at the equator, reflecting the fact that the uppermost regolith layer is consistently fine-grained and fluffy almost everywhere. The physical structure of the top few centimeters is dominated by the cumulative effects of tiny micrometeorite impacts grinding the surface into powder over billions of years.2Journal of Geophysical Research: Planets. Lunar equatorial surface temperatures and regolith properties from the Diviner Lunar Radiometer Experiment
Morning and Evening Are Not Symmetrical
You might expect the surface to warm and cool in a neat mirror image on either side of noon, but it does not. At the equator, the ground near the dusk terminator (the line where day turns to night) is about 30 K warmer than the ground near the dawn terminator (where night turns to day).1Icarus. The global surface temperatures of the Moon as measured by the Diviner Lunar Radiometer Experiment This asymmetry exists because the regolith stores heat during the long day. By sunset, the upper layers have had two weeks of solar baking and still retain warmth. By dawn, they have had two weeks to radiate that heat away. So even though both terminators sit at the same Sun angle, their thermal histories are very different.
This matters practically. A spacecraft or rover landing just after sunrise would touch down on a surface that has been cooling for two weeks and is near its minimum temperature. A landing just before sunset encounters ground that is still warm from prolonged heating. Mission planners factor this thermal asymmetry into landing-site selection and hardware survival strategies.
Rocks Glow Warmer Than Dust
The headline nighttime temperature of about −178°C applies to the typical dusty surface, but not everything cools at the same rate. Exposed rocks and boulders have much higher thermal inertia than loose regolith: they absorb more heat during the day and release it more slowly at night. Areas with high rock abundance can be more than 50 K warmer than the surrounding zonal average during the night.1Icarus. The global surface temperatures of the Moon as measured by the Diviner Lunar Radiometer Experiment In practical terms, a boulder field at night might sit around −130°C rather than −180°C. That is still frigid, but the difference is significant for thermal modeling and for understanding how rock breakdown works on the Moon.
These temperature swings put real mechanical stress on lunar boulders. Modeling of the thermomechanical response shows a two-phase stress pattern over each day-night cycle. At sunrise, rapid heating of the surface creates steep temperature gradients against the still-cold interior of a boulder, producing interior stresses. At sunset, the rapidly cooling and contracting outer shell creates stresses at the surface. In a one-meter boulder, both types of stress reach around 10 megapascals, and larger boulders experience proportionally greater forces, suggesting they break down faster than small ones.3Icarus. Thermally induced stresses in boulders on airless body surfaces, and implications for rock breakdown Over millions of years, this thermal fatigue gradually fractures boulders into smaller pieces, contributing to the deep regolith layer that blankets the entire Moon.
Dark Plains Versus Bright Highlands
Not all lunar terrain absorbs the same fraction of sunlight. The dark volcanic plains known as maria have lower albedo than the brighter, more heavily cratered highlands. This albedo difference produces a daytime temperature gap of about 5–10 K between the two terrain types. The effect also shows up in microwave radiometer data from China’s Chang’E-2 orbiter, which confirmed that darker maria run hotter during the day, though differences in the electrical properties of the surface material can partially offset the gap by a few degrees in the opposite direction.4Icarus. High frequency thermal emission from the lunar surface and near surface temperature of the Moon from Chang’E-2 microwave radiometer
A 5–10 K difference does not sound dramatic when the overall day-night swing is hundreds of degrees, but it matters for remote-sensing scientists who use surface temperature to infer composition. If you are trying to map what the Moon is made of using infrared data, you need to account for the fact that some temperature variation comes from what the surface is rather than just where the Sun is in the sky.
The Polar Cold Traps
The most extreme cold on the Moon is not at the equator during the night but near the poles, inside permanently shadowed craters. Because the Moon’s rotational axis is tilted only about 1.5 degrees relative to the plane of its orbit around the Sun, the floors of certain deep craters near the north and south poles never receive direct sunlight. These permanently shadowed regions, or PSRs, act as cold traps where temperatures can plunge far below the equatorial nighttime minimum.
Diviner measurements have confirmed that large areas of the south polar region are cold enough to trap water ice, and also cold enough to trap other volatile compounds that are both more and less volatile than water.5Science. Diviner lunar radiometer observations of cold traps in the moon’s south polar region Some of the coldest measured spots dip below 40 K (about −233°C or −387°F), among the coldest naturally occurring temperatures in the entire solar system. Separate modeling work has identified areas cold enough to serve as carbon dioxide cold traps, which require even lower temperatures than water ice to remain stable.6Geophysical Research Letters. Carbon Dioxide Cold Traps on the Moon
Interestingly, the subsurface temperatures in these near-polar craters are somewhat warmer than older thermal models predicted. Recent modeling with updated thermal conductivity values found that subsurface temperatures in permanently shadowed regions are about 5–10 K warmer than earlier estimates, while cooler nighttime surface temperatures were observed globally.7Journal of Geophysical Research: Planets. A Global Thermal Conductivity Model for Lunar Regolith at Low Temperatures A few degrees may sound trivial, but for determining whether ice is stable at a given depth, it makes a real difference. The question of exactly how much water ice exists in these cold traps is one of the driving scientific questions behind upcoming missions to the lunar south pole.
Lava Tubes and Collapsed Pits
Perhaps the most surprising thermal environment on the Moon is found underground. The Moon has lava tubes, hollow tunnels left behind by ancient volcanic flows, and collapsed pits that open into subsurface voids. These sheltered spaces behave nothing like the wild surface. Observations and thermal modeling of equatorial pits suggest that the permanently shadowed areas beyond a pit’s opening maintain a nearly constant temperature of about 290 K (roughly 17°C or 63°F), close to comfortable room temperature on Earth.8Geophysical Research Letters. Thermal and Illumination Environments of Lunar Pits and Caves: Models and Observations From the Diviner Lunar Radiometer Experiment
That 17°C figure has attracted enormous interest from engineers designing future lunar habitats. While the sunlit floor of a pit can still reach over 150°C (above 420 K), the shaded portions deeper inside are shielded from direct solar radiation and from the extreme radiative cooling of the open surface. The surrounding rock mass acts as a thermal buffer, absorbing and releasing heat slowly enough to smooth out the savage temperature swings happening overhead. Researchers who have reviewed collapsed caves on the Moon found that shadowed cave interiors showed temperatures ranging between about −20°C and 30°C, compared to the −170°C to 110°C range measured on the exposed surface nearby.9International Journal of Mining Science and Technology. A comprehensive review of lunar lava tube base construction and field research on a potential Earth test site Direct measurements from inside intact lava tubes have not yet been possible, but the thermal stability inferred from pit observations and modeling makes these sites leading candidates for future outposts.
Heat Trickling Up From Below
The Moon is not thermally dead on the inside. It still produces a small amount of internal heat from the decay of radioactive elements in its mantle. Measurements from the Apollo-era heat flow probes, combined with more recent gravity data, suggest a mantle heat flux of roughly 9–13 milliwatts per square meter, corresponding to a total mantle heat production on the order of a few hundred billion watts.10Journal of Geophysical Research: Planets. Lunar heat flow: Regional prospective of the Apollo landing sites That might sound like a lot stated in watts, but spread across the entire Moon it is vanishingly small compared to the solar energy hitting the surface. The internal heat flow has essentially no effect on surface temperatures in any human-relevant timescale. Where it does matter is in understanding conditions tens of centimeters to meters below the surface, and in reconstructing the Moon’s thermal evolution over billions of years.
Keeping Hardware Alive Through the Night
For robotic missions, surviving the two-week-long lunar night is one of the toughest engineering problems. At equatorial landing sites, surface temperatures during the night drop well below what most electronics and batteries can tolerate without damage. China’s Yutu-2 rover, which has operated on the far side of the Moon, enters a hibernation mode during each lunar night, relying on a radioisotope heater to keep its core systems from freezing.
One proposed approach involves deployable thermal shelters: lightweight, folding covers made of multi-layer insulation that a rover could unfurl over itself before nightfall. Modeling of both single- and double-cover designs showed that such a shelter could reduce heat loss from the rover by up to about 22%, potentially enough to keep critical components above their survival thresholds during the long, cryogenic night.11Acta Astronautica. Thermal shelter for survival of rover during cryogenic lunar night A 22% reduction in heat loss does not sound transformative on its own, but when the alternative is carrying a heavy nuclear heat source or simply not operating at night, lightweight passive solutions become attractive.
The thermal environment also affects how lunar dust behaves around equipment. Near the terminator, where the transition from sunlit to shadowed ground creates steep thermal gradients over short distances, local electric fields build up on the surface. These fields can be strong enough to levitate fine dust particles, on the order of one micrometer in size, particularly just after sunset near the terminator line.12Planetary and Space Science. Charging and motion of dust grains near the terminator of the moon This electrostatically lofted dust was reported by Apollo astronauts who noticed a strange glow on the lunar horizon around sunrise and sunset. For future equipment and habitats, thermally driven dust transport is a maintenance headache that adds to the already punishing thermal cycling.
Why Shadows on the Moon Are So Different From Earth
On Earth, stepping into the shade on a hot day might drop the temperature you feel by a few degrees. On the Moon, the difference is dramatic. Without an atmosphere to convect heat or scatter light, the shadowed side of a rock or a crater wall can be hundreds of degrees colder than the sunlit side just centimeters away. There is no wind to mix warm and cold air because there is no air. Energy transfers only by radiation and by conduction through the ground, both of which are slow processes compared to atmospheric convection.
Inside permanently shadowed regions, the only warmth arrives indirectly: infrared radiation emitted by nearby illuminated surfaces and sunlight reflected off crater walls. Research into the lighting conditions of permanently shadowed areas has found that the infrared emission from the illuminated surface is roughly equal in total intensity to the reflected visible sunlight that reaches the shadowed zone.13Acta Astronautica. The spectral radiance of indirectly illuminated surfaces in regions of permanent shadow on the Moon Even with both sources combined, the energy reaching the floor of a deep permanently shadowed crater is a tiny fraction of what direct sunlight would deliver, which is why these spots get so extraordinarily cold.
This sharp thermal contrast between illuminated and shadowed surfaces has practical implications for anyone designing structures or choosing landing sites. A solar panel left in permanent shadow produces nothing. A piece of equipment sitting half in sun and half in shadow experiences a temperature gradient across its body that can warp metal and stress joints. Mission designers have to think not just about average conditions but about these extreme local contrasts that have no real parallel on Earth.