The record low, measured on the East Antarctic Plateau, which includes the South Pole, didn’t identify a particular date, but rather relied on analyzing data captured by satellites between 2004 and 2016 to show that this low temperature occurs whenever the conditions are right.

It beat out the previous lowest land temperature measured by a ground station on July 23, 1983, at Vostok Station in Antarctica. It also exceeded the previous satellite-based estimate of -135°F using a similar approach in 2013.

Researchers think a lower temperature on our planet is unlikely—maybe a smidge lower with unusual conditions.

In an article in Geophysical Research Letters, researchers from several institutions led by Ted Scambos, senior research scientist at the National Snow and Ice Data Center at the University of Colorado-Boulder, discovered that with the right conditions, temperatures plunge well below previous expectations after days of extremely clear skies, light wind, and very dry air.

At a couple of miles above sea level (about 3,500m), on top of the ice sheet covering the East Antarctic Plateau—near the Vostok Station measurement, in fact—the temperature is routinely below -130°F (-90°C). However, super-dense, super-cold pockets of air descend and become trapped in tiny depressions, just 6 to 9 feet deep. This very low-temperature air allows the snow in these hollows to radiate even more heat, allowing for the extraordinarily low ground temperature.

This new research combined data from several NASA satellites, including one that had been recalibrated in 2016 with new information from ground stations.

The researchers believe it would require weeks, rather than days, of clear skies to provide any further reduction in air temperature that would allow the snow to cool off even further in those depressions.

However, they’ve designed new ground measurement equipment capable of dealing with the extreme cold, which they plan to deploy in the next two years.