Lake Peipsi is one of the largest lakes in Europe and is totally covered with ice almost every winter. We introduce a thermodynamic ice model built for the investigation of ice seasons on Lake Peipsi. Long-time data from the Estonian national hydro-meteorological network on the air temperatures, wind speed and direction, and ice thickness and duration were used to develop and test the model. We ran the model for severe, normal, and mild winter conditions. Ice cover monitoring is complemented with ice maps derived from MODIS 250-m resolution images.