Even at –25 °C, it can still drizzle rather than snow.

Israel Silber at Pennsylvania State University in University Park and his colleagues spotted supercooled drizzle at this temperature in August 2016, in clouds above the McMurdo Station research base near the Ross Ice Shelf in Antarctica. The drizzle lasted for more than 7.5 hours.

The scientists used lasers and radar to probe Antarctic clouds. By measuring how the instruments’ signals scattered off cloud particles, the researchers could tell that the water was liquid.

In very cold clouds, water usually freezes around dust particles to form ice. The authors suggest that, in this case, there were probably too few dust particles in the air for ice to form. As a result, the water remained liquid as it fell through the sky.

Supercooled drizzle has been spotted at a few other places on the planet. But it might be widespread over Antarctica and the Southern Ocean, because those regions have just the right combination of low dust levels and chilly temperatures.