A combination of cold air in the sky and radiational cooling due to lack of cloud cover on December 19 resulted in 15 of the 22 observation points in the Okhotsk region recording the lowest temperatures of the season. Minus 18.7 degrees was recorded in the town of Bihoro, while mid-winter temperature in line with average temperatures in late January and early February were also recorded throughout the region.

　Elsewhere, it was minus 18.6 degrees in the town of Tsubetsu, and minus 18.0 degrees in the city of Kitami, where, on the same morning, diamond dust (fine ice) – which tends to occur on clear days when the temperature drops below minus 10 degrees – and sun pillars, which look like pillars of sunlight, appeared on fields of snow. In addition, these phenomena also coincided with a phenomenon known as a ‘halo,’ in which a large circle of light forms around the sun due to thin cloud cover.