Little research has examined seasonal differences in physical activity (PA) levels among children. Proxy reports of PA were completed by 1,715 parents on their children in Edmonton, Alberta, Canada. Total PA (TPA) minutes were calculated, and each participant was classified as active, somewhat active, or inactive. Logistic regression models were conducted to examine associations between PA status and seasons. Significant seasonal differences were observed for TPA, weekday PA, weekend PA, and active play. Children were significantly more likely to be physically active in the summer and spring and somewhat physically active in the summer and fall, relative to winter Children living in cold climates are less likely to be physically active in the winter.