The paper is devoted to the identification of transmission lines from synchronized measurements of current and voltage phasors provided by the phasor measurement units (PMUs). The series and shunt line parameters are recursively estimated using the extended Kalman filter (EKF). Actual line temperature and reference resistance are estimated instead of actual series resistance, which is then computed from these estimates. This approach can accommodate more information and, therefore, produce better estimates of the line resistance than the traditional approaches based on the weighted least squares method. Two case studies based on data from South Moravia and East Bohemia are presented to demonstrate the effectiveness of the proposed approach.