Cotton (Gossypium hirsutum L.) yield variability over time is determined by weather and agronomic factors in site-specific soil conditions. Plant density is among the most important agronomic practices in cotton production. However, the relative importance of each factor remains unclear. Here, we addressed plant density effects and the relative importance against weather factors on yield variability over time using a decade-long (2008–2017) field experiment on cotton crops that consisted of a wide range of plant densities from 1.5 to 10.5 plants m^–2 in the Yellow River Valley of China. The results showed that a plant density of 3.3 plants m^–2 produced stable productivity across periods of contrasting weather conditions. However, the average plant density for maximum yield was 5.9 plants m^–2. As such, there was a trade-off between yield potential and yield stability for cotton crops. Moreover, plant density and weather explained 46.4 % and 29.1 %, respectively, of the variation in cotton yield during 2008–2017. Among weather related factors, air temperature during the growing season had stronger independent explanatory power (25.8 %) than did sunshine hours (5.1 %) and annual precipitation (1.3 %). Taken together, our results not only highlight the importance of focusing on yield stability for sustainable agricultural management recommendations but also underline the necessity of considering the primary weather variations for accurately predicting agricultural yield under climate change.