i will try to explain in a brief report the climate in bulgaria.
Bulgaria as a whole is considered to be in a moderate climate zone. There are two distinct climate zones with the Stara Planina Mountain being the watershed between them. One of the country's best features is the distinct four seasons that they experience as well as the favorable climate year-round.
Winter: Winters are colder in Northern Bulgaria and much milder in the Southern part of the country. Winter temperatures vary between 0° and 7°C below zero. temperatures may drop below 20°C below zero.
Spring: The spring climate is typical continental and changeable. It provides a favorable environment for the growth of the growth of the native fruit-bearing trees whose fruit is has been renowned in Europe for centuries.
Summer: Summer is hot and sweltering in Northern Bulgaria, especially along the Danube River. The climate in Southern Bulgaria is determined by the air-currents from the Mediterranean.
Summer temperatures do not reach the extremes as in Dobrudzha and along the Danube and are usually moderate: about 28°-30°C. The highest readings are usually taken in the towns of Rousse and Silistra, sometimes reaching above 35°C.
Autumn: Autumns are mild and pleasant in Bulgaria. The multi-coloured forests in autumn add to the picturesque landscape. Autumn showers are more frequent than in spring. May, October and November are the rainiest months.
Annual average rainfall is about 700 mm, more in the mountains (up to 1000 mm and more) and less on the coast (around 400-600 mm). It can rain throughout the year; in general, winter is the driest season. In summer, showers and thunderstorms are common, especially in the mountains.
Quoted from different sources specially from Villa Stresov and weatheronline