A study was conducted at Los Baños, Laguna to determine the degree of correlation among productive and physiological responses of local lactating dairy cows with climate variability. From an average of 10 lactating Holstein-Sahiwal dairy cows, the monthly average milk yield, dry matter intake, pulse rate (P), respiration rate (R) and body temperature (T) at 0700, 1100, and 1500 h for 4 consecutive days per month were gathered from September 2011 to June 2012. Heat Index (HI) was calculated from the climatic data from PAGASA Weather Station at UPLB. Correlation analysis was performed to determine the degree of linear relationships between milk yield and dry matter intake, PRT values, environmental temperature, relative humidity, and HI. Milk yield was highly correlated (P<0.05) with HI (r=-0.73), environ-mental temperature (r = -0.71), dry matter intake (r = -0.64), and pulse rate (r=-0.68). The effect of increasing HI value (x) on milk yield (Y) is described by the equation: Y = 25.6 –0.189x (R2=0.535; P<0.05). This indicates that HI negatively influenced milk yield of lactating cows. Further studies are needed to determine the interrelationships of PRT, HI and milk yield for the formulation of adaptive mechanisms to avoid economic loss from decreased milk yield due to heat stress.