an SI Tour℠

Most recent addition: 11 December 2020

All boiling points are measured at standard atmospheric pressure (101,325 pascals) unless otherwise stated.

IPTS-68 = International Practical Temperature Scale of 1968; ITS-90 = International Temperature Scale of 1990.

Temperature in
  Not yet observed
Temperature in
  Not yet observed
Temperature in
  Not yet observed
Temperature in
  Not yet observed
Temperature in
450 ± 80

Photo of researchers in front of machine.

Tom Pasquini (left) and Aaron Leanhardt in front of the machine that cooled atoms to 450 picokelvins.

Courtesy Ketterle Lab, MIT

Sodium gas cooled at MIT, 2003.

A. E. Leonhardt, T. A. Pasquini, M. Saba, A. Schirotzek, Y. Shin, D. Kielpinski, D. E. Pritchard and W. Ketterle.
Cooling Bose-Einstein Condensates below 500 picokelvin.
Science, vol 301, no. 5839, pages 1513-1515 (12 September 2003).

Temperature in

Graph of state of rubidium atoms

Courtesy Mike Matthews and UC Boulder.

Rubidium atoms cooled at the University of Colorado at Boulder, 10:54 am 5 June 1995. First production of a Bose-Einstein condensate.

M. H. Anderson, J. R. Ensher, M. R. Matthews, C. E. Wieman and E. A. Cornell.
Observation of Bose-Einstein condensation in a dilute atomic vapor.
Science, vol. 269, page 198 (14 July 1995).

Temperature in
~360 Aluminum membrane cooled by "squeezed" laser light.

Jeremy B. Clark, Florent Lecocq, Raymond W. Simmons, Jose Aumentado and John D. Teufel.
Sidebrand cooling beyond the quantum backaction limit with sqieezed light.
Nature, v541, 191-195 (12 January 2017)

~400 First successes in cooling large numbers of molecules to ~400 µK that did not involve combining precooled atoms.

E. B. Norrgard, D. J. McCarron, M. H. Steinecker, M. R. Tarbutt and D. DeMille.
Submillikelvin Dipolar Molecules in a Radio-Frequency Magneto-Optical Trap.
Physical Review Letters, vol 116, no. 6, 063004 (10 Feb 2016).

Strontium monofluoride.

Alexander Prehn, Martin Ibrügger, Rosa Glöckner, Gerhard Rempe and Martin Zeppenfeld.
Optoelectrical Cooling of Polar Molecules to Submillikelvin Temperatures.
Physical Review Letters, vol 116, no 6, 063005 (10 Feb 2016)


Temperature in
2 Below this temperature, helium-3 is a superfluid.

D. D. Osheroff, R. C. Richardson, and D. M. Lee.
Evidence for a New Phase of Solid He3.
Physical Review Letters, vol. 28, no. 14, pages 885–888 (1972)

6 Inner chamber of the detector built by the Cryogenic Underground Observatory for Rare Events in Gran Sasso, Italy. Temperature maintained for 2 weeks in 2014. Though described as "the coldest cubic meter in the universe," the actual operating volume is about 636 liters.

Jonathan L. Ouellet.
The coldest cubic meter in the known universe.
arXiv:1410.1560v2 [physics.ins-det] 14 Oct 2014

20 Operating temperature of the Edelweiss-III detectors in Modane, France, an attempt to detect WIMPs.
Temperature in

Photo in polarized light of the Boomerang Nebula

Hubble Heritage Team, J. Biretta (STSci) et al., (STSci/AURA),ESA,NASA

Expanding carbon monoxide gas pouring, at 164 kilometers per second, from a dying star in the Boomerang Nebula.
Perhaps the coldest spot in the universe, outside of laboratories.

Raghvendra Sahai and Lars-Åke Nyman.
The Boomerang Nebula: The coldest region of the universe?
Astrophysical Journal Letters, vol 487, no. 2, L155 (1997 Oct 1)
doi: 10.1086/310897

1.95 Estimated temperature of the Cosmic Neutrino Background, formed when the universe was 2 seconds old.
2.17 Below this temperature, helium-4 becomes a superfluid.
2.72548 ± 0.00057

Map of cosmic background radiation

Cosmic microwave background

D. J. Fixsen.
The temperature of the cosmic microwave background.
The Astrophysical Journal, vol. 707, no. 2, page 916 (30 November 2009).

4.2 Highest temperature at which mercury is a superconductor.
4.2 Boiling point of helium-4 at atmospheric pressure. (For helium-3, it is 3.2 K.)
5 - 7 Large dust particles in the protoplanetary disk of gas and dust around star 2MASS J16281370-2431391

Photo of the star 2MASS J16281370-2431391.

The "Flying Saucer"

Courtesy ESO.

S. Guilloteau, V. Piétu, E. Chapillon, E. Di Folco, A. Dutrey, T. Henning, D. Semenov, T. Birnstiel and N. Grosso.
The shadow of the Flying Saucer: A very low temperature for large dust grains.
Astronomy & Astrophysics Letters, 586, L1 (2016).
doi: 10.1051/0004-6361/201527620

9.26 Antimatter cooled at the CERN laboratory, 2010. A record low.
13.8033 Triple point of H2 (ITS-90). (Was a primary reference point in IPTS-68, at 13.81 K.)
17.042 Hydrogen boils at a pressure of 33,330.6 pascals. (Was a primary reference point in IPTS-68)
20.28 Hydrogen boils. (Was a primary reference point in IPTS-68)
24.5561 Triple point of neon (ITS-90).

false-color image of temperatures near the Moon's north pole

Southwestern edge of Hermite crater, near the Moon’s north pole (the lavender areas in the image). Measured in 2009 by the Diviner Radiometer on NASA’s Lunar Reconnaissance Orbiter. Touted as the “coldest known place in the solar system.”
27.102 Neon boils. (A primary reference point in IPTS-68)
50 Surface of the minor planet Pluto.
54.3584 Triple point of O2 (ITS-90)
56 Surface of the planet Neptune.
58 Surface of the planet Uranus.
70 to 110

Rings of Saturn by temperature.


Rings of Saturn. In this false-color image from the Cassini spacecraft, blue is 70 kelvins, green is 90 kelvins, and red is 100 kelvins.
83.8058 Triple point of argon. (ITS-90) (Was 83.798, a primary reference point in IPTS-68)
90.188 Oxygen boils. (A primary reference point in IPTS-68)
97 Surface of the planet Saturn.
104.3 Antimatter cooled at Harvard University, 1989. A record low at that time.
129 Surface of the planet Jupiter.
135 Highest temperature at which yttrium barium copper oxide remains a superconductor.
180.0 East Antarctica Plateau, 10 August 2010. Temperature of surface as measured by satellite. Lowest air temperature recorded on Earth (by 2013)

www.nasa.gov/content/goddard/nasa-usgs-landsat-8-satellite-pinpoints-coldest-spots-on-earth/ Great video.

184 Vostok, Antarctica, 21 July 1983

John Turner, Phil Anderson, Tom Lachlan-Cope, Steve Colwell, Tony Phillips, Amélie Kirchgaessner, Gareth J. Marshall, John C. King, Tom Bracegirdle, David G. Vaughan, Victor Lagun, Andrew Orr.
Record low surface air temperature at Vostok station, Antarctica.
Journal of Geophysical Research, vol. 114, D24102, (2009).


Carbon dioxide pellets sublimating.

Carbon dioxide pellets used in the wine industry. The white "smoke" coming from them is not carbon dioxide vapor, which is colorless and transparent, but clouds formed by water vapor condensing as the dry ice and cold carbon dioxide vapor chill the air.

©iStockphoto.com/Hèlène Vallèe

Solid carbon dioxide (dry ice) turning to vapor. (A secondary reference point in IPTS-68.)
205.4 Verkhoyansk, 2 May 1892, and Oimekon, 6 February 1933, both in northeastern Siberia, Russia, a tie for lowest air temperature recorded by 2013 in the northern hemisphere, or in any permanently inhabited place.
207.1 North Ice, Greenland 21 July 1983, lowest air temperature recorded in the western hemisphere by 2010.
210.2 Snag, Yukon Territory, Canada, 3 February 1947. Lowest air temperature recorded in North America by 2010.
215.05 Ust 'Schugor, Russia, 31 December 1978. Lowest air temperature recorded in Europe by 2010.
218 Surface of the planet Mars.
229 Lowest temperature at which microdroplets of water remained fluid.

J. A. Sellberg, C. Huang, T. A. McQueen, N. D. Loh, H. Laksmono, D. Schlesinger, R. G. Sierra, D. Nordlund, C. Y. Hampton, D. Starodub, D. P. DePonte, M. Beye, C. Chen, A. V. Martin, A. Barty, K. T. Wikfeldt, T. M. Weiss, C. Caronna, J. Feldkamp, L. B. Skinner, M. M. Seibert, M. Messerschmidt, G. J. Williams, S. Boutet, L. G. M. Pettersson, M. J. Bogan and A. Nilsson.
Ultrafast X-ray probing of water structure below the homogeneous ice nucleation temperature.
Nature, vol. 510, pages 381–384 (19 June 2014)

230 On Ellesmere Island, Canada, the high arctic woolybear caterpillar (Gynaephora groenlandica), survives hibernation at this temperature.
230.65 Lowest temperature reached for supercooled water.

Claudia Goy, Marco A. C. Potenza, Sebastian Dedera, Marilena Tomut, Emmanuel Guillerm, Anton Kalinin, Kay-Obbe Voss, Alexander Schottelius, Nikolaos Petridis, Alexey Prosvetov, Guzman Tejeda, Jose M. Fernandez, Christina Trautmann, Frederic Caupin, Ulrich Glasmacher and Robert E. Grisenti.
Shrinking of rapidly evaporating water microdroplets reveals their extreme supercooling.
Physical Review Letters, 120.015501 (2 January 2018)

234.3156 Triple point of mercury. (ITS-90) (In IPTS-68, mercury freezing was a secondary reference point at 234.288 K.)
240.4 Samiento, Argentina, 1 June 1907. Lowest air temperature recorded in South America by 2010.
249.3 Ifrane, Morocco, 11 February 1935. Lowest air temperature recorded in Africa by 2010.
250.2 Charlotte Pass, New South Wales, Australia, 29 June 1994. Lowest air temperature recorded in Australia by 2010.
273.16 Triple-point of water, by definition. The temperature at which water can simultaneously exist in liquid, solid, and gaseous forms. (ITS-90)
288 Surface of the planet Earth. (Some say 255K.)
288.2 Vanda Station, Antarctica, 1 May 1974. Highest air temperature recorded in Antarctica by 2010.
300.02 Phenoxy benzene (diphenyl ether) triple point, a secondary reference point in IPTS-68.
301.59 Cesium melts.
302.9146 Gallium melts. (ITS-90)
310 Typical human body temperature.
312.45 Rubidium melts.
315.4 Tuguegarao, Philippines, 29 April 1912. Highest air temperature recorded in Oceania by 2010.
315.75 In Oman, 26 June 2018, daily minimum temperature, the highest recorded to that date.
321.2 Athens and Elefsina, Greece, 10 July 1977. Highest air temperature recorded in Europe by 2010.
322.1 Rivadavia, Argentina, 11 December 1905. Highest air temperature recorded in South America by 2010.
323 The Saharan silver ant Cataglyphis bombycina, survives 10 minutes foraging in the desert at this temperature.

Walter J. Gehring and Rudiger Wehner.
Heat shock protein synthesis and thermotolerance in Cataglyphis, an ant from the Sahara desert.
Proceedings of the National Academy of Sci. USA, vol. 92, pages 2994-2998 (March 1995).

R. Wehner and A. C. Marsh.
Desert ants on a thermal tightrope.
Nature, vol. 657, issue 6397 (18 June 1992).

323.9 Oodnadatta, Australia, 2 January 1960. Highest air temperature recorded in the southern hemisphere by 2010.
327 Mitribah, Kuwait on 21 July 2016
327.1 Tirat Tsvi (Tirat Zevi), Israel 21 June 1942. Highest air temperature recorded in Asia by 2010.
327.55 Death Valley, California 16 August 2020.

Salt pan near Furnace Creek Ranch.

©iStockphoto.com/Steve Geer

Furnace Creek Ranch, California, USA, 10 July 1913. Highest air temperature recorded in the western hemisphere by 2010, and recognized by WMO. However, later researchers have questioned the data. Reid and Burtthis link goes to another website.
331 El Azizia, Libya, 13 September 1922. Highest air temperature recorded on Earth as of 2010.
336.53 Potassium melts.
370±40 Coolest known brown dwarf star, CFBDSIR J1458+1013B, as of 2011.

Michael C. Liu, Philippe Delorme, Trent J. Dupuy, Brendan P. Bowler, Loic Albert, Etienne Artigau, Celine Reyle, Thierry Forveille and Xavier Delfosse.
CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System.

370.87 Sodium melts.
373.15 Water boils at standard pressure. (A primary reference point in IPTS-68)
394 Record high temperature for an organism to live and reproduce: a microorganism dubbed strain 121, collected from a “black smoker”, an active oceanic hydrothermal vent on the Juan de Fuca Ridge in the northeast Pacific. (It was not the 121st organism tested; the name comes from the Celsius temperature, 121°C, i.e., 394 K, at which they were cultured.) DNA analysis showed the species belongs to the domain Archaea. It survived 2 hours at 403 K, but without reproducing.

Kazem Kashefi and Derek R. Lovley.
Extending the Upper Temperature Limit for Life.
Science, vol. 301, p. 934 (15 August 2003).
doi: 10.1126/science.1086823

394 Temperature to which most medical autoclaves are set, to sterilize instruments.
395.52 Benzoic acid triple point. (A secondary reference point in IPTS-68.)
429.7485 Indium freezes. (ITS-90) (In IPTS-68, freezing indium was a secondary reference point at 429.784 K)
440 Surface of the planet Mercury.
453.65 Lithium melts.
505.078 Tin freezes. (ITS-90) (Was a primary reference point in IPTS-68 at 505.1181 K)
527 Polonium melts.
540 ± 40 Brown dwarf UGPS 0722-05, 13.3 light years from Earth, discovered 2010.

P. W. Lucas, C. G. Tinney, Ben Burningham, S. K. Leggett, David J. Pinfield, Richard Smart, Hugh R. A. Jones, Federico Marocco, Robert J. Barber, Sergei N. Yurchenko, Jonathan Tennyson, Miki Ishii, Motohide Tamura, Avril C. Day-Jones, Andrew Adamson, France Allard and Derek Homeier.
The discovery of a very cool, very nearby brown dwarf in the Galactic plane.
Monthly Notices of the Royal Astronomical Society,

544.55 Bismuth melts.
577 Thallium melts.
594.22 Cadmium melts. (In IPTS-68, freezing cadmium was a secondary reference point at 594.258 K.)
600.61 Lead melts. (In IPTS-68, freezing lead was a secondary reference point at 600.652 K.)
630 Mercury boils. (In IPTS-68, freezing mercury was a secondary reference point at 629.81 K.)
653 Water issuing from a hydrothermal vent on the seafloor (East Pacific Rise, off Baja California)
692.677 Zinc freezes. (ITS-90) (Was a primary reference point in IPTS-68 at 692.73 K)
730 Surface of the planet Venus.
800 Midlatitude temperatures on Jupiter.
903.78 Antimony melts.
913 Plutonium melts.
917 Neptunium melts.
923 Magnesium melts.

Pouring molten aluminium.

©iStockphoto.com/Mary Ann Shmueli

Aluminum freezes. (ITS-90) (In IPTS-68, freezing aluminum was a secondary reference point at 933.61 K.)
973 Radium melts.
Temperature in
1.00 Barium melts.
1.05 Strontium melts.
1.07 Cerium melts.
1.092 Ytterbium melts.
1.095 Europium melts.
1.1 to 1.3 Rhyolite lava.
1.115 Calcium melts.
1.180 Zinc boils.
1.191 Lanthanum melts.
1.204 Praseodymium melts.
1.23493 Silver freezes. (ITS-90)
(Was a primary reference point in IPTS-68, at 1.23508 K)
1.294 Neodymium melts.
1.3 to 1.5

Lava in Hawaii.

©iStockphoto.com/Loic Bernard

Erupting basaltic lava (for example, at Kilauea, Hawaii)
1.315 Promethium melts.
1.324 Actinium melts.

Pouring molten gold.

©iStockphoto.com/Steve Lovegrove

Gold freezes. (ITS-90)

(Was a primary reference point in IPTS-68, at 1.33758 K.)
1.347 Samarium melts.
1.35777 Copper freezes. (ITS-90)
1.408 Uranium melts.
1.519 Manganese melts.
1.560 Beryllium melts.
1.58 Over the Great Red Spot on Jupiter.

J. O’Donoghue, L. Moore, T. S. Stallard and H. Melin.
Heating of Jupiter’s upper atmosphere above the Great Red Spot.
Nature, vol. 536, pages 190–192 (11 August 2016)

1.586 Gadolinium melts.
1.629 Terbium melts.
1.685 Dysprosium melts.
1.728 Nickel melts.
1.747 Holmium melts.
1.768 Cobalt melts.
1.795 Ytterbium melts.
1.802 Erbium melts.

Pouring molten iron.

©iStockphoto.com/Greg McCracken

Iron melts.
1.814 Scandium melts.
1.818 Thulium melts.
1.828 Palladium melts.
1.845 Protoactinium melts.
1.89 The mineral olivine begins to crystallize out of a pure olivine melt.
1.936 Lutetium melts.
1.941 Titanium melts.
2.023 Thorium melts.
2.04155 Platinum melts.
2.128 Zirconium melts.
2.180 Chromium melts.
2.183 Vanadium melts.
2.237 Rhodium melts.
2.430 Technetium melts.
2.506 Hafnium melts.
2.607 Ruthenium melts.
2.719 Iridium melts.
2.750 Niobium melts.
2.835 Copper boils.
2.896 Molybdenum melts.
3.129 Gold boils.
3.200 Cobalt boils.
3.290 Tantalum melts.
3.306 Osmium melts.
3.459 Rhenium melts.
3.62 Daylight side of the planet WASP-33b, hottest planet found (as of 2011).

A. M. S. Smith, D. R. Anderson, I. Skillen, A. Collier Cameron and B. Smalley.
Thermal emission from WASP-33b, the hottest known planet.
http://arxiv.org/abs/1101.2432 (11 June 2011)

3.695 Tungsten melts.
4.098 Platinum boils.
5.5 The sun's photosphere.
5.828 Tungsten boils.
5.869 Rhenium boils.
4.5 to 10



The sun’s chromosphere.

Lightning bolt.

©iStockphoto.com/Marinico Tarlac

Lightning bolt. Typical initial temperature in return-stroke center channel.
50 Blue supergiant star.

Planetary nebula surrounding white dwarf star.

The white dwarf is seen near the center.


White dwarf star HD62166, in NGC 2440.
Temperature in
1 to 1.8

Mass ejection in sun's corona.


The sun’s corona.
15 The sun's core.
50 - 100 Expected operating temperature of plasma in the Mega Amp Spherical Tokamak in the UK.
150 Expected operating temperature of plasma in ITER in France.
Temperature in
4 A quark-gluon plasma made by colliding gold ions at speeds near that of light at the Brookhaven National Laboratory’s Relativistic Heavy Ion Collider. The blob was about 100 nanometers across and lasted for a little more than 1 attosecond. The temperature was estimated by measuring the average wavelength of photons emitted by the plasma (like measuring the temperature of a skillet from the infrared it emits). To compensate for the fact that the blob was cooling, researchers calculated backwards to estimate its peak temperature.
200 Core of the supernova 1987A, during collapse, estimated from neutrinos.
Temperature in
5.5 A collision between lead nuclei at the Large Hadron Collider, CERN, Switzerland, on 13 August 2012. Quark-gluon plasma. Highest temperature reached in a laboratory at time of writing (2015), often described as highest temperature anywhere in present-day universe.


Temperature in
Temperature in
Temperature in
Temperature in
1,416,683,300 The Planck temperature, the temperature of a body by virtue of which it emits radiation with a wavelength of the Planck length. As hot as it gets, in the standard theory.

for further reading

Tom Shachtman.
Absolute Zero and the Conquest of Cold.

Mark S. Blumberg.
Body Heat: Temperature and Life on Earth.
Cambridge; Harvard University Press, 2002.

Gino Segrè.
A Matter of Degrees: What Temperature Reveals about the Past and Future of Our Species, Planet, and Universe.
New York: Viking, 2002.

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