The record
−89.2 °C (−128.6 °F), Vostok Station, Antarctica, 21 July 1983.
Vostok sits at about 3,500 metres on the East Antarctic plateau, in the middle of the continent, in the middle of the polar night. Every ingredient for extreme cold is present at once: high altitude, thousands of kilometres from any ocean, an ice surface that reflects almost all incoming sunlight, and months of darkness in which the surface can do nothing but radiate heat to space.
It has stood for over forty years as the coldest air temperature reliably measured at the surface of the Earth.
The colder numbers people quote
Since 2010, satellite studies of the East Antarctic plateau have reported values near −94 °C (−137 °F) in small hollows on the ice.
Those numbers are real, and they are not air temperatures. A satellite measures the infrared radiation leaving a surface, which gives you the temperature of the snow itself. On a clear polar night the snow surface radiates heat away and ends up colder than the air above it — the same effect that puts frost on a lawn while the official reading stays above freezing, described in at what temperature frost forms.
So there are two honest statements. The coldest air temperature ever measured is −89.2 °C. The coldest surface temperature ever measured is around −94 °C. Mixing them produces the confusion you see whenever this comes up.
The records that are comparable
| Place | Temperature | When |
|---|---|---|
| Vostok Station, Antarctica | −89.2 °C (−128.6 °F) | July 1983 |
| Oymyakon, Russia | −67.7 °C (−90 °F) | February 1933 |
| Verkhoyansk, Russia | −67.7 °C (−90 °F) | February 1892 |
| Greenland ice sheet | −66.1 °C (−87 °F) | January 1954 |
| Snag, Yukon, Canada | −63 °C (−81.4 °F) | February 1947 |
| Prospect Creek, Alaska | −62 °C (−80 °F) | January 1971 |
| Rogers Pass, Montana | −57 °C (−70 °F) | January 1954 |
| Mount Washington, New Hampshire | −44 °C (−47 °F) | January 1934 |
What every one of these places has in common
Read the list and the same features recur.
Altitude. Air cools with height, so an elevated plateau starts colder than sea level before anything else happens.
Distance from the ocean. Water has enormous thermal mass and moderates the air above it. Continental interiors have nothing buffering them and swing much further in both directions.
Snow and ice cover. Fresh snow reflects most of the sunlight that reaches it, so even when the sun is up it delivers little warmth to the surface.
Long clear nights. Extreme cold is not something that happens quickly. It is the result of a surface radiating heat to space for weeks with almost nothing coming back.
Terrain that traps air. This is the one people miss, and it explains the Siberian entries. Oymyakon and Verkhoyansk sit in valleys where cold dense air drains downhill and pools with nothing to scour it out. A settlement can be dramatically colder than the region around it — the mechanism is a temperature inversion, on a valley-sized scale.
Where the scale runs out
Absolute zero is −273.15 °C (−459.67 °F), the point at which there is no thermal energy left to remove. It is the zero of the kelvin scale, and it cannot be reached — though laboratories have come within a whisker of it, far colder than anywhere in the natural universe including deep space.
Between the Antarctic record and absolute zero sits a long stretch of temperatures that only occur artificially: dry ice, liquid nitrogen, liquid helium. That ordered scale is sub-zero, dry ice and liquid nitrogen.
These figures are the most extreme reading ever taken at each place, often decades ago and sometimes with instruments that would be reassessed today. A record says what was once possible at one spot on one night. It says almost nothing about whether that place is getting colder or warmer, which is a question about averages over decades.
Putting the number in scale
−89.2 °C is difficult to feel, so a few anchors on the way down:
- −18 °C (0 °F) — a domestic freezer.
- −40 °C (−40 °F) — the one point where Celsius and Fahrenheit agree.
- −62 °C (−80 °F) — the Alaskan record.
- −78.5 °C (−109 °F) — dry ice sublimes.
- −89.2 °C (−128.6 °F) — Vostok, 1983.
- −196 °C (−321 °F) — liquid nitrogen boils.
- −273.15 °C (−459.67 °F) — absolute zero.
Vostok's record sits between dry ice and liquid nitrogen, which is the fact worth carrying away: the coldest air ever measured on Earth is colder than the dry ice used to keep ice cream frozen in transit.