This study aimed to analyze the cloudiness cover characteristics associated with heavy precipitation events in northwest Iran. For this purpose, daily precipitation data from 19 synoptic stations located in the study area over a 20-year period (2000–2019) were used. In order to evaluate the cloud cover characteristics, ERA5 reanalysis data were obtained and for the analysis of heavy precipitation events, days that met the criteria of intensity (99th percentile of precipitation) and spatial extent (coverage of at least 30% of stations) were identified. For each identified event, three cloud cover indices were calculated, including cloud cover intensity (TCC), cloud spatial extent based on the area of the region with (TCC ≥ 0.7), and also the spatial pattern of the cloud cover center of mass. The results of the validation of ERA5 using MERRA-2 data showed that this database has a good performance in representing the cloud cover characteristics associated with heavy precipitation events. Based on the analysis, in 50% of the heavy precipitation events, the center of mass of the spatial pattern of clouds was located southeast of Tabriz station, and in the same proportion, the cloud spatial extent (TCC ≥ 0.7) was recorded as 1 and complete cloud cover (100%). The maximum cloud spatial coverage among the 16 heavy precipitation events was related to the event of 03/02/2006, while the minimum cloud spatial extent of 0.43 was observed in the event of 03/03/2018. Event-based analysis of cloudiness can provide a more accurate understanding of the role of the spatial structure of cloud systems in the formation of heavy precipitation in the region. The coincidence of the maximum extent of cloudiness with intense heavy precipitation events indicates the importance of continuous cloud cover in intensifying precipitation.