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Field experiments were conducted for two years (2005-06 and 2006-07) at IARI, New Delhi, India research farm to assess the variations of micrometeorological parameters under differential hydrothermal regimes in mustard crop. Changes in sowing time and branch removal/defoliation treatments were imposed in order to create variations in hydrothermal regimes under phenology based irrigation scheduling. It was inferred that near-ground surfaces in the debranched plot where microenvironment was modified, air temperatures were higher (2 to 3 degrees C) as compared to control plots, decreased at 35 cm and remained almost similar with further increase in height at 1130 hrs while at 1430 hrs the magnitude of temperature variations was relatively higher. In contrast to air temperature, the relative humidity in debranched plot was less than that of the control plot. At near-ground, even at higher canopy height about 10% higher RH variations were observed in control plot as compared to debranched plot both in morning and afternoon hours. Furthermore, leaf area index could explain variations in temperature and RH to the tune of 40-50%. Radiation penetration and soil moisture depletion pattern also indicated significant impact of microclimatic variations near the ground.