Weather authorities in Bulgaria have issued a Code Yellow alert for 17 of the country's 28 regions on Monday, days before sub-zero temperatures start to rise.

The regions affected by the lowest warning (currently issued for low temperatures) are Vidin, Montana, Vratsa, Pleven, Lovech, Gabrovo, Veliko Tarnovo, Targovishte, Ruse, Razgrad, Silistra, Dobrich, Shumen, Pernik, Kyustendil, Sofia-city and Sofia-region.

January 24 is said to have been the coldest day of the year, with night thermometers in some northwestern regions hitting minus 22 to minus 28 degrees Celsius (the latter value was recorded in Knezha, a northwestern town known for "traditionally" low temperatures in the winter).

On Monday temperatures in Western and Northern Bulgaria are expected to remain below zero, ranging between a negative 10-15 and a negative 1-4. In the south, maximum temperatures will be from minus 6-7 degrees to 4-5 degrees in the southernmost regions.

Mild winds from the northwest will bring about a rise in air temperature from Tuesday on, with clouds dispersing over parts of the country but also with dense fogs expected in Northern Bulgaria's Danube region.