Climate experts stationed at an Argentine research base in a northern part of Antarctica have just logged the highest temperature on record for the typically frozen continent.

According to preliminary data from the U.N.’s World Meteorological Organization, temperatures on the Antarctic Peninsula just hit 64.9 degrees Fahrenheit, or 18.3 degrees Celsius. That figure tops the previous record of 17.5 degrees Celsius set in March 2015.

While such temperatures might be considered pleasant under different circumstances—say on a picnic or hiking trip—this is Antarctica we’re talking about, home to the most inhospitable environments on the planet.

Rising temperatures are alarming there because Antarctica, for one thing, contains the vast majority of Earth’s freshwater ice, along with Greenland.

Moreover, according to the WMO, temperatures in this particular area have warmed some 3 degrees Celsius over the last 50 years, and 87% of the nearby glaciers have retreated during that period.

Worse, the retreat is accelerating. And when glaciers melt, bad things happen: Ice flowing from Antarctica’s Thwaites Glacier, for example, is thought to be a major contributor to sea-level rise.

Some climatology experts on Twitter are referring to this week’s warm temperatures as a “heat wave,” which is not a word you want to hear associated with Antarctica.