The aim of this study is to determine the relationship between the occur¬rence of a sea breeze (SB) and cumulonimbus (Cb) clouds over the Istrian Pe¬ninsula. For this purpose, available standard surface measurements, i.e., the near-surface wind, the air and sea surface temperatures and cloudiness at two stations (Pula-Airport and Pazin), and satellite images were analyzed. The study was performed during the summer months (from June to September) for the years 1997–2006. The analysis showed that the Cb development was typically associated with certain meteorological conditions. These conditions were as follows: (i) SB speed at Pula-Airport in the range of 3–5 m s–1, (ii) maxi¬mum temperature difference between sea and land near Pula-Airport around 4 °C, and (iii) maximum air temperature in Pazin in the range of 25 to 31 °C. On average, during the days with simultaneous development of SB and Cb clouds, the land breeze was weaker and the air temperature was higher than on other analyzed days. Diurnal cloud evolution showed that Cb clouds usually develop (above Pazin) between 13 and 14 h of Central European Time (CET). Cumulus clouds, as indicators of the SB inland penetration, preceded the Cb development. Satellite images for 2000–2006 obtained by the geostationary satellites Meteosat 7 and 8 were investigated, and a spatial distribution and a temporal development of 30 chosen Cb events were detected. Two characteris¬tic regions of the Cb origin were noted: the northern and southeastern parts of the Istrian Peninsula. The Cb clouds usually formed between 11 and 13 CET, lasting in general from 3 to 5 hours and disintegrating between 15 and 17 CET.Cilj je ove studije odrediti vezu između pojave smorca i kumulonimbusa (Cb) nad Istrom. Pritom se koriste raspoloživa standardna prizemna mjerenja, kao što su prizemni vjetar, prizemna temperatura zraka, površinska temperatura mora i naoblaka na dvije postaje (zračna luka Pula i Pazin) te satelitske slike. Analiza koja se vršila za ljetne mjesece (od lipnja do rujna) u razdoblju 1997.–2006. je pokazala da je Cb razvoj učestaliji u određenim meteorološkim uvjetima. Oni su bili: (i) brzina smorca na postaji zračna luka Pula u intervalu od 3–5 m s–1, (ii) maksimalna temperaturna razlika između kopna i mora oko 4 °C u blizini zračne luke Pula i (iii) maksimalna temperatura zraka u Pazinu u intervalu od 25 do 31 °C. U usporedbi s drugim analiziranim danima, kopnenjak je bio nešto slabiji i temperatura zraka je bila viša onih dana kada je registrirana istovremena pojava SB i Cb nad Istrom. Dnevni razvoj oblaka je pokazao da se Cb oblak uobičajeno razvija nad Pazinom izme|u 13 and 14 h po srednjeeuropskom vremenu. Kumulusni oblaci povrh i ispred SB fronte, (koja je indikator prodiranja morskog zraka u unutra{njost), prethodili su Cb razvoju. Satelitske slike u razdoblju 2000.–2006. dobivene geostacionarnim satelitima Meteosat 7 i 8 su pokazale prostornu razdiobu i vremensku evoluciju 30 odabranih slučajeva Cb razvoja. Uočena su dva karakteristična područja nastanka Cb: sjeverni i jugoistočni dio Istre. Oblaci Cb tipa se uobičajeno formiraju između 11 i 13 h po srednjeeuropskom vremenu, traju od 3 do 5 sati te nestaju između 15 i 17 h po srednjeeuropskom vremenu
