Soybean [Glycine max (L.) Merr.] is an important source of health-beneficial compounds, including soyasaponin I. A field study was conducted for 11 yr in Ottawa, ON, Canada, to assess the impacts of temperature and precipitation during specific growth stage intervals on soyasaponin I concentration in three soybean cultivars. Soyasaponin I concentration response to air temperature and precipitation variables were observed at specific growth stage intervals for some cultivars. The response was complex and cultivar specific. Overall, reproductive stages were more responsive and 20 °C appeared to be a critical threshold in determining soybean soyasaponin I concentration response to air temperature.