This article presents research focused on improving dimensional accuracy and reducing thermal deformations in Fused Deposition Modeling (FDM) 3D printing by locally supplying additional heat in the form of a directed stream of hot air to the product shaping zone. The experiments were conducted using two materials: PET-G and ABS. Dimensional accuracy was evaluated by comparing the actual dimensions of the printed models with the dimensions of the CAD model, with the differences interpreted as height deviations. The deviations obtained during printing without additional airflow were compared to those obtained when using post-heating with air at a temperature of 95 °C. The results showed that the height deviations (H1 and H2) were reduced when using the heated air stream, especially for PET-G and ABS. These promising results indicate the potential for further development of this method. Future work will focus on investigating various parameters of heat delivery to the printed surface, including temperature, flow rate, application speed, and the distance from the nozzle to the heat source. The long-term goal is to develop guidelines for improving the geometric accuracy of prints produced on 3D printers that do not have a heated build chamber.