Up to recently, suspended solids and petroleum products were considered the most environmentally threatening contaminants in stormwater from urban areas. Since the early 2000s, there has been a steady upward trend in the concentration of nutrients (nitrogen and phosphorus) in stormwater. Moreover, the concentration of nitrogen and phosphorus in stormwater began to exceed the concentration of these elements in natural water bodies and created a serious environmental threat to natural hydrosphere bodies, as it served as a factor in their eutrophication. Experimental studies have shown a persistent increase in the concentration of ammonium nitrogen in the water of the Kharkiv and Lopan rivers in the section below the city, which indicates that river water is polluted by stormwater runoff from the territory of Kharkiv. We have analyzed the ammonium nitrogen contamination of winter season stormwater runoff (melted snow) generated in Kharkiv and its suburbs. The level of ammonium nitrogen pollution of atmospheric snow was determined and the influence of snow exposure on the level of its ammonium nitrogen pollution was investigated. According to the data obtained, there is an active increase in the concentration of ammonium nitrogen in snow in the city compared to its content in atmospheric snow. Even in the yards closed from the impact of motor vehicles, the concentration of ammonium nitrogen in the snow increased by 3.5 times, and in the roadside area of the intersection – by more than 4 times. Absolute concentrations of ammonium nitrogen in the snow were 2–4 times higher than the MPC for wastewater discharge into natural water bodies (2 mg/l).