Understanding how climate extremes affect crop growth in humid-subtropical hilly regions is essential for climate-smart agriculture, yet phenology-resolved evidence remains limited. We combined 20 ETCCDI extreme climate indices (1960-2024) with field records of wheat and maize production (2005-2024) from the hilly area of southwest China, and quantified climate-crop linkages using Mantel tests and generalized additive models; persistence and prospective tendencies were evaluated using Hurst (H) and Mann-Kendall statistics. Warming extremes intensified, with significant increases in TXx (0.22 degrees C decade-1), SU25 (2.48 days decade-1), and DTR (0.47 degrees C decade-1), while TNx and TNn declined and frost days increased; most precipitation intensity indices showed no significant trends except CDD, which increased by 1.73 days decade-1. Seasonally, warm extremes and CDD strengthened during the maize season, whereas climatic conditions during the wheat season were comparatively more favorable. Climate impacts on crop growth were stage-dependent, typically lagging by 1-2 months: wheat biomass was positively associated with TXx/TNx (strongest near heading), whereas maize production was more sensitive to temperature extremes (negative) and precipitation frequency indices; CDD significantly affected both crops. These findings suggest that compound heat-drought risks for maize could increase under the persistence and trend signals observed in the historical record, while modest warming may benefit wheat but cold extremes could remain a constraint for management.