Winters in Sliven are cold and unpredictable, with temperatures often dropping below freezing point in January and February. March marks the beginning of spring, with temperatures gradually warming up, but still ranging between -7°C and 20°C. The warmest months are May to August, with average highs reaching up to 25-31°C during these periods, while September brings a slight cooling trend. Autumn is mild, with October and November averaging around 8-11°C, before the cold winter sets in again. Overall, Sliven's climate is characterized by significant temperature fluctuations throughout the year.