Behavior of free-ranging cows was investigated as affected by season, diurnal periods, and weather parameters. Sixteen genetically diverse lactating cows were fitted with vibracorders to record active time continuously from 18 May 1989 to 3 January 1990. Total collection time was divided into three seasons: hot-dry (1 June to 12 July), warm-rain (1 August to 11 September), and cold-dry (1 November to 12 December). Days within seasons were divided into 24 1-hour periods. Differences in active time were found among seasons (P < .05), periods (P < .05), periods within seasons (P < .05), and cows within periods within seasons (P < .05). Activity was lowest during the hot-dry season during darkness. Substantial activity occurred during the hottest daytime periods. Warm-rain season activity during darkness increased (P < .05) slightly with daytime period activity increasing substantially (P < .05). Cold-dry season activity illustrated classical grazing periods with major post-dawn, pre-dusk, and nighttime period activity. Average total daily active times were 10.9 h, 12 h, and 9.5 h for hot-dry, warm-rain, and cold-dry seasons, respectively. Cows were very active during the hot periods of the day during the hot-dry season. Lowest total active time occurred during the cold-dry season when cows were not lactating and had low physiological requirements.