Photo/IllutrationRed-crowned cranes fly in the middle of fog in Tsurui in eastern Hokkaido on Feb. 9. (Nobuhiro Shirai)

RIKUBETSU, Hokkaido--With Japan's northernmost main island locked in a deep freeze caused by the coldest air mass ever recorded here, the temperature plunged to a frigid minus 31.8 degrees in Rikubetsu in eastern Hokkaido on Feb. 9.

That marked a new low in Japan this season, as three other observation spots in Hokkaido also reported temperatures below minus 30 degrees.

Temperatures in Kushiro and nine other sites hit record lows.

In Tsurui village, also in eastern Hokkaido, a school of red-crowned cranes gracefully took flight in a fantastical fog, called “kearashi,” which is created when steam rising from a river meets cold air.

The birds, designated as a special natural treasure by the central government, are wintering in Tsurui where the national feeding ground was set up.