Context: Canola (Brassica napus L.) is a key rotational crop in Mediterranean-type dryland farming systems, yet its yield is highly sensitive to rainfall variability and temperature extremes. Objective: This study aimed to evaluate the influence of rainfall and temperature factors on canola yield across phenological stages and provide guidance for cultivar selection and adaptive management. Methods: Twelve years (2011-2023) of field trial data from the Swartland region of South Africa were analysed, including 13-18 canola cultivars per season classified by cultivar type (conventional, Clearfield, and Triazine Tolerant) and growing season length (short, medium-short, medium, and long). Yield data were analysed using a three-way analysis of variance (ANOVA), Pearson correlations, and both linear and quadratic regression models to identify critical climate-yield relationships. Results: The ANOVA detected main and interaction effects among cultivar type, season length, and year (P < 0.05 for all main effects). Triazine Tolerant cultivars consistently yielded less than conventional and Clearfield cultivars. Short and medium-short cultivars performed better under drier conditions, while medium-length cultivars excelled in seasons with early planting and favourable late-season moisture. Correlation analyses indicated that yield was strongly and positively associated with rainfall amount and frequency during vegetative and flowering stages, as well as with moderately warm temperatures during the seedling stage. Conversely, high average temperatures and heat stress events during flowering and pod filling were negatively correlated with yield. Multiple regression models confirmed the significance of these relationships, and quadratic regressions highlighted stage specific nonlinear thresholds for rainfall and temperature effects. Yield gains plateaued beyond 300 mm seasonal rainfall, while optimal flowering stage rainfall was between 90-110 mm. Average temperatures above 13 degrees C during flowering and 15 degrees C during pod filling consistently reduced yield. Heat stress during flowering, even as few as one day exceeding 28 degrees C, was especially detrimental. Cumulative growing degree days to flowering and end of flowering were positively related to yield, but growing degree days to maturity showed weaker associations. Conclusion: Canola yield is shaped by stage specific climatic sensitivities, particularly to rainfall distribution and reproductive stage heat stress. Implications: Climate-smart cultivar selection and planting strategies that align growth stages with optimal rainfall and temperature windows will be essential to sustain canola productivity under intensifying climate variability.