Tree-to-wire discharge represents a prevalent cause of transmission line failures, significantly compromising the safety and stability of power transmission systems. The pre-arcing discharge phenomenon, which persists as an extended pre-breakdown phase prior to arcing between vegetation and conductors, offers critical opportunities for early risk mitigation and fault prevention. This study focuses on this discharge phase, establishing a simulated experimental platform to investigate hazard discharge characteristics under varying relative positions of vegetation growth near conductors through the introduction of offset distance parameters. Experimental results reveal distinctive discharge signatures of tree-line hazard discharge. Based on these findings, a risk assessment model is developed for vegetation proximity states surrounding single-phase 35 kV conductors under idealized conditions, elucidating distinct challenges associated with different tree species and seasonal variations. Furthermore, comprehensive consideration of sag and wind-induced sway effects yields an enhanced risk model for vegetation proximity states around 35 kV conductors, accompanied by corresponding boundary trajectory equations. These outcomes provide theoretical references for vegetation-induced hazard identification and optimized vegetation management within transmission corridors.