The National Institute of Meteorology and Hydrology (NIMH) issued yellow code alert for cold weather for sixteen regions of Bulgaria on Thursday.
The warning is issued for the regions of Dobrich, Gabrovo, Lovech, Montana, Pernik, Pleven, Razgrad, Ruse, Shumen, Silistra, Sofia, Sofia province, Targovishte, Veliko Tarnovo, Vidin and Vratsa.
In nine of these regions a yellow code for dense fogs has also been issued.
The minimum temperatures in these regions will be minus 15 and minus 10 degrees, with the maximum temperatures also to remain below zero.
The weather will be mostly sunny and slightly warmer than on Wednesday.
In the Danube plain and parts of western Bulgaria it will be foggy, with visibility expected to improve around midday.
The maximum temperatures in northern Bulgaria will range between minus 6 and minus 1 degrees, while those in the southern part of the country will be between 0 and 5 degrees.