Cereal rye (Secale cereale L.) cover crop provides a multitude of benefits, including soil conservation and weed suppression. Cereal rye biomass is positively correlated with weed suppression; however, high biomass is not always feasible. The weed-suppression potential of cereal rye grown under conditions that do not support high biomass is unknown. In such cases, other mechanisms, such as reduced soil temperature and nutrient depletion, may contribute to weed suppression. The objective of this study is to determine the impact of cereal rye biomass levels on soil water, temperature, nutrients, and, in turn, weed emergence patterns. Cereal rye was planted at four seeding rates (0, 20, 40, and 80 kg ha-1) and terminated at three timings (6, 4, and 2 weeks before planting cotton). Soil water and temperature were continuously monitored using automatic sensors. Soil nutrient content was analyzed from samples taken before cereal rye planting and at each termination timing. Weed seedling emergence was assessed throughout the summer. Cover crop termination timing had a greater influence on biomass production than seeding rate; delaying termination by four weeks resulted in 70 to 150% more biomass. High cereal rye biomass levels reduced maximum soil surface (0-10 cm) temperature by up to 7 C and thermal amplitude by 10 C before crop planting. Cereal rye significantly reduced soil nitrogen content but had minimal effect on phosphorus and potassium. A minimum biomass production of 2 t ha-1 is necessary for 30-50% weed suppression, whereas moderate (2 to 4 t ha-1) and high biomass levels (6000 kg ha-1) provided 60-70% and >90% weed suppression, respectively. The time for 50% weed seedling emergence was delayed by 18 days under high cereal rye biomass compared to fallow. Overall, our findings indicate that cereal rye suppresses weeds through multiple mechanisms, explaining suppression even at low biomass levels.