Abstract: Based on multi source observations, ERA5 high-resolution reanalysis data, and operational model forecast data, this paper analyzes the extreme characteristics, occurrence, and development mechanisms and predictability of an abnormal temperature increase event in the Beijing–Tianjin–Hebei region from February 17 to 21, 2021. The results indicate that during this period, more than 90% of the stations in the region exceeded the historical February temperature extremes. Daily maximum and minimum temperatures exceeded 24°C, with the southern Hebei region recording a peak temperature of 28°C. Key contributing factors included a weakened polar vortex in the early stages and the persistent “－＋－” circulation pattern, which provided favorable conditions for extreme warming. The results show that the advection and perpendicular terms primarily contributed to the event, whereas the nonadiabatic heating term had minimal impact. Short- and medium-term forecasts performed effectively for this abnormal warming event. Specifically, the National Centers for Environment Prediction (NCEP) and intelligent grid deterministic forecasts showed high accuracy within 36 h, especially for plain areas. The control forecasts by European Center for Medium Range Weather Forecasts (ECMWF) and China Meteorology Administration (CMA) global ensemble members demonstrated skill in predicting the 500-hPa geopotential height 9 and 5 days in advance, respectively. Furthermore, the predictability limit of the ensemble average forecast extended 1–2 days beyond the control forecast. However, for periods extending beyond 2 weeks, the reference provided by the ensemble monthly dynamic extended model for the circulation situation was notably less reliable.