The present work presents a seasonal balance of the frequency of participation of these systems in the region of Santa Maria, Rio Grande do Sul, whose results were obtained by the analysis of the regional circulation . This analysis focused on the year 1973, selecting, in the larger temporal segment, the standard year representative of the usual for the central region of the State. It was evidenced that the control of the weather, in said region, is imposed by the Extratropical Systems due to their greater participation in number of days (334), to the detriment of the Inter Tropical Systems (31 days), demonstrating the predominance of the Fronts and Polar Masses in the regional atmospheric circulation. The Extratropical Systems operated, practically,
