In terms of climate, Pernik is within the temperate continental climate zone. Only the Vitosha slope is in the mountain climate zone. The relatively big average height above sea level – 750 meters, which varies within a broad range – from 650 to over 2000 meters, determines the climatic conditions. The ground-level temperature inversions are a characteristic feature of the climate, especially during the winter months.
Spring comes relatively late, about the end of March or the beginning of April. The average spring temperature is +9°C.
Summer isn’t hot, and the average temperature for the season is 19.9°C. July is the hottest month, its average monthly temperature being 29.6°C. The absolute temperature maximum value is 38.1°C.
Autumn is warmer than spring. The average temperature for the season is 10°C. September has the highest average monthly temperature – 16.1°C.
When there are western or southwestern winds, which are prevalent, foehn is observed on the northern slopes of Golo Bardo. It is most typically observed in springtime.
The number of foggy days in the year is relatively large – about 28.8. There are about 2.5 foggy days in the warm half of the year and about 26.3 in the cold half.
Precipitations are of a markedly continental nature. They play an important role in the process of pollution and self-purification of the atmosphere. The amount of precipitations, along with the relatively low summer temperatures, are the main causes for the summer droughts being less severe than in the lowlands of Northern and Central Bulgaria. The average yearly precipitations amount is 550 to 606 mm. The average precipitation amount for each season is, as follows: Spring – 162 mm., summer – 165 mm., autumn – 152 mm., winter – 128 mm. May is the most humid month of the year. March is the month with least precipitations amount.
The comparatively large precipitation amount is a favorable factor for the self-purification of the atmosphere. However, it decreases the diffusion and leads to an increased burden on the soil and the surface waters.