Bulgaria as a whole is sutiated in the moderate climatic zone. The country can be conditionally divided into two climatic zones. The Stara Planina Mountain is considered the watershed between them. 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. Very rarely temperatures may drop below 20°C below zero. Typical continental and changeable is the climate in spring. It is exceptionally favourable for the growth of fruit-bearing trees, for whose fruit Bulgaria has been renowned in Europe for centuries. 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 Dobroudzha 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. Autumns are mild and pleasant in Bulgaria. The multi-coloured forests in autumn add to the picturesque landscape. Autumn showers in principle are more frequent than in spring. May, October and November are the rainiest months.
As is natural, in the high mountains the temperatures depend on the altitude. There are different climatic zones suitable for the growth of one or another rare species or crops. Typical examples are the Sub-Balkan valley, referred to as the Rose Valley, some regions in the Rhodope Mountains where one can find the unique flower of Orpheus, the region of the town of Sandanski where olives and citrus fruit are grown, etc.
There are some interesting areas from a climatic point of view, such as the Sofia Plain, the regions of Sliven and Varna, where strong winds blow almost throughout the year. In the first two cases they are due to the proximity with the Balkan Mountains and its passes, which let all winds blow constantly through them. In the case with Varna this phenomenon is due to the specific microclimate of the Bay of Varna and the sea air-currents coming from the north.
