The Ministry of Environment has warned of expected rise of river water levels mainly in western and central Bulgaria on Wednesday.
Local flash floods due to intensive rainfalls are also possible.
Bulgaria's Institute for Meteorology and Hydrology forecast for Wednesday is for rainfalls in many parts of the country, more excessive in the eastern Bulgarian Burgas region.
Bulgaria's Ministry of Environment and Waters warned of possible overflowing of major rivers flowing through the northern part of the country.
Due to the expected heavy rains in the upcoming days, the rivers Ogosta, Iskar and Yantra – tributaries of the Danube – might overflow and cause floods, said the ministry, quoting the European Flooding Awareness System (EFAS).