The influence of air temperature on herbicides Aminopielik D 450 SL (2,4-D=417.5 g/l+dicamba=32.5 g/l) and Mustang 306 SE (2,4-D=300 g/l+florasulam 6.25 g/l) was investigated in controlled climate chambers. Three temperature levels: 25/16.5, 16.5/8 and 8/2°C, were tested while the relative humidity and light intensity were constant for all the temperature regimes. P. rhoeas was used as the test plant and treated with the herbicides at 2- to 4-leaf stage. At the time of harvest (3 weeks after herbicide treatment), fresh weight was determined. Temperature influenced the weed growth and herbicide efficacy. P. rhoeas produced the greatest biomass at 25/16°C. The efficacy of both herbicides was significantly reduced at the lowest temperature level (8/2°C). The highest temperature (25/16°C) differentiated the activity of Mustang 306 SE, irrespective of dose level. A similar effect was observed at 8/2°C after Aminopielik D 450 SL application.