Per- and polyfluoroalkyl substances (PFAS) are persistent and toxic contaminants commonly detected in surface water, yet their occurrence and seasonal dynamics in ice-covered surface waters in winter are poorly understood. This study investigated the occurrence of 40 PFAS in the surface waters in North Dakota during winter through three tiers of sampling campaigns. First, in the Red River, total PFAS concentrations Σ[PFAS] were 1.5 times higher on average during winter at 17.4 ng·L-1 than in summer at 11.9 ng·L-1. Spatially, PFAS concentrations were high at near-bank and surface locations, with long-chain hydrophobic compounds showing the greatest enrichment under ice-covered conditions. Second, in the statewide samples around contamination sites during snowmelt across North Dakota, Σ[PFAS] ranged from 7 to 2235 ng·L-1, and the contamination was strongly source-dependent. The sites near air force bases (AFBs) were dominated by long-chain perfluoroalkyl sulfonic acids (PFSAs), while sites near wastewater treatment plants and municipal airports were dominated by perfluoroalkyl carboxylic acids (PFCAs). Snowmelt concentrations were up to 97 times higher than those reported in the statewide summer survey. Third, the two source waters for drinking water plants also showed 1.5−2.8 times higher Σ[PFAS] during winter than summer. Overall, PFAS contamination in the surface waters of cold regions was more severe during winter ice-covered and spring snowmelt seasons than in summer. Thus, it is important to monitor winter and snowmelt concentrations for accurate characterization of PFAS occurrence and protection of drinking water sources.