As a result of atmospheric circulation processes and the complex physical-geographical environment, year-round climatic conditions in Tbilisi Gorge are very diverse. High ranges, located to the west of the city, prevent the penetration of western air masses into the gorge. Therefore the influence of western (wetter) winds here is very weak, and they reach the city with much less moisture than when they started. This is the main cause of dryness of air and low precipitation. When very cold air masses from the west penetrate the city, temperatures drop and precipitation increases. Dry air masses blowing from the east, are responsible for little amount of precipitation on a bottom of the gorge. However, in a higher zone on foothills average amount of precipitation is notably more. The temperature drops rapidly if there is a penetration of Arctic air masses from the East.
Relief forms have a significant influence on climatic conditions here, as the city is surrounded by mountains on three sides. Only the eastern part is comparatively low and open towards the Caspian Sea. The difference between highest and lowest points here is about 500 m. This causes some climatic 'vertical zonation': Mean annual temperatures within the region vary from 10.80 to 12.60. In the low zone the annual temperature is higher than on surrounding mountains and foothills. The coldest month in Tbilisi Gorge is January with a temperature of 0.50 on a bottom and -0.7 0 on hills and mountains. The warmest month is July, when the temperature varies from 21.50 to 24.20. On hills and mountains the warmest month of the year is August (21.60 to 22.1 0). The maximum temperatures within the city sometimes reach 380 (July-August). Distribution of precipitation on the bottom, foothills and mountains of the gorge is not the same. Mean annual precipitation is 510 mm in the city centre, only 450 mm in Digomi Valley, and 525 mm in Ortachala. Generally the eastern part of the city is drier (440 mm annually). Maximum precipitation is in May with the following distribution: in the city centre - 88 mm., in Vaziani (eastern edge of Tbilisi) - 93 mm., in Digomi - 79 mm., in Karsani (foothills of Trialeti Range) - 104 mm. Another maximum is usually in September, when monthly amounts of average precipitation are almost half of May levels. The driest months are January (10-26 mm.) and August.