Sugarcane is a long-duration crop whose growth is strongly governed by the interplay of climatic factors operating across its successive phenophases. The present investigation was undertaken at Parikshitgarh, Meerut, Uttar Pradesh, during 2024–25, to study the effect of climatic factors during different phenophases on the growth of the early-maturing sugarcane cultivar Co 0238, planted on 23–24 March 2024 and harvested on 20–21 February 2025. The crop duration was divided into four phenophases — germination, tillering, grand growth, and maturity/ripening — and monthly climatic data (temperature, rainfall, relative humidity, sunshine hours and wind speed,) were correlated with monthly growth parameters (plant height, tiller number, millable shoot number, Leaf Area Index, green leaf number, cane girth, internode number, and dry matter accumulation). Correlation of monthly growth increments (rather than cumulative values) with the corresponding month's climatic factors showed that structural growth attributes — plant height, cane girth, internode formation, and LAI — were strongly and positively associated with mean temperature (r = 0.66–0.88, p<0.05 to p<0.01), consistent with the known optimum temperature range of 30–35°C for sugarcane vegetative growth. Rainfall and rainy days showed the strongest positive association with internode formation and canopy parameters, while tiller and millable shoot increment were most strongly (negatively) associated with relative humidity, reflecting the self-thinning of non-productive tillers coinciding with the monsoon canopy-closure period. The results confirm distinct phenophase-specific climatic sensitivity in Co 0238 and provide a quantitative basis for weather-informed agronomic planning of early-maturing sugarcane cultivars in western Uttar Pradesh.