The "Hydrometeorology and Monitoring Center" SNCO presents the advisory weather forecast for December.
"The average monthly air temperature throughout the republic is predicted to be 1-2 degrees above normal, and the amount of precipitation is less than usual.
In December, the sun's height above the horizon continues to decrease in the Northern Hemisphere, and therefore, the duration of daylight decreases.
The duration of sunshine during the month is 110-120 hours. Cold air currents from the northern latitudes predominate in the republic's atmospheric circulation. Severe frosts are most common when cold air from Western Siberia or Scandinavia invades our country.
The average monthly temperature in the republic in December is -3.9°C. In high mountain regions at altitudes of 2000 m and above sea level, average monthly temperatures are pretty low: -6...-11°C.
The coldest month of winter is January, but in 18-20% of winters, it is December. As a rule, the lowest temperature in December occurs in the third decade of the month, but in some cases, for example, in 1984, it happened in the first decade in the northeastern regions. The coldest Decembers were followed in 1953, 1970, 1982, 1984, 1987, 2002, when the average monthly temperature was 6-8 degrees below normal. The historical minimum temperature in December in the republic was recorded in 1948 in Ashotsk, where the air temperature dropped to -40 °C at night.
December 2002 was characterized by a very low thermal regime: air temperatures decreased day by day in the second half of the month, reaching their lowest values on December 28. The minimum temperature in the Ararat Valley was -32°C, and in Yerevan, -28°C; both exceeded historical minimums. The warmest Decembers were observed in 1938, 1940, 1966, 1980, 1981, 1998, and 2008. In those years, the maximum temperature in the Ararat Valley and Yerevan reached +21...+22°C, and in the lowlands of Tavush and Syunik +24...+26°C.
Relative humidity in December is relatively high - 70% and more. The average amount of precipitation is 38 mm. The lowest precipitation is observed in the lowlands of the Ararat Valley and in the southeast, up to 20 mm.
In the coastal regions of Lake Sevan, it reaches 20-25 mm; in the foothills, 30 mm; in the mountainous areas, 60 mm; and in the high mountainous regions, 80-90 mm. The wettest Decembers in the republic were observed in 1946, 1956, 1958, 1969, 1987, 2003, when the amount of precipitation was 200-300% of the monthly norm, the driest Decembers were observed in 1911, 1947, 1961, 1980, 1995, 1999, 2004, when no precipitation was recorded in the valley regions of the republic at all.
Precipitation is mainly observed in the form of snow. In mountainous areas, snow cover reaches 20-30 cm, and in the republic's warm regions, stable snow cover does not form in the first and second decades of December.
Calm weather prevails, and high wind speeds are observed in the mountains and mountain passes. Maximum speeds reach 18-20 m/s, gusts reach 25 m/s. Frequent fogs characterize December. Fog is most often observed in the Ararat Valley, Syunik, and Shirak. December 2013 and 2016 were also freezing and foggy in the Ararat Valley and Yerevan, due to the stagnation of cold air. The fog that appeared in December 2016 persisted until the first ten days of March 2017. On December 21, the winter solstice occurs, when the longest night and shortest day are observed in the northern hemisphere, after which the duration of daylight gradually increases.
