Constructed wetlands have been widely used for managing urban stormwater runoff and improving stormwater quality. However, the removal efficiency of nutrients in these systems varies significantly. To investigate the nutrient removal behaviors and the influencing factors in constructed wetlands, two wetlands (Rocky Ridge "RR" and Royal Oak "RO") in Calgary, Alberta, Canada, were selected for field monitoring in the open-water seasons of 2018 and 2019. It was found that the annual loading removal efficiency of total nitrogen in the RR wetland was 37 % and 64 % in 2018 (dry year) and 2019 (wet year), respectively, while in the RO wetland it was 45 % and 33 %, respectively. The annual loading removal efficiency of total phosphorus in the RR wetland was 34 % and 44 % in 2018 and 2019, respectively, while in the RO wetland it was 57 % and 75 %, respectively. The annual nutrient mass removal (in mg/m2/yr) in the wet year was substantially (7-16 times for TN; 7-29 times for TP) larger than that in the dry year for the same wetland, mainly attributed to the significantly larger inflow volume in the wet year. Further analysis showed that large rainfall events increased nutrient concentrations in both inflow and outflow, leading to variations in removal efficiency. The outflow concentration was primarily affected by inflow in large rain events but by in-pond water in small events. The study highlights seasonal and interannual variations, emphasizing the role of environmental parameters in nutrient removal. Finally, the unique aspects of nutrient removal by cold-regions stormwater wetlands are discussed.