The purpose of study was to compare the effects of lower and higher (by ±3ºC) air temperature in the poultry house in the period from 28 to 42 days of the growing period with the standard (medium) air temperature conditions in Ross 308 and Hybro G commercial broilers chickens, taking into consideration the main performance traits of birds and quality of carcase and meat. The experimental findings demonstrated that increasing or decreasing standard air temperature in the poultry house by ±3ºC significantly deteriorated the examined performance traits. A higher negative effect on the physicochemical traits of muscles was noted in the case of higher air temperature. It pertained mainly to the degree of muscle acidification post mortem and intramuscular fat content. The studied ambient air temperatures influenced to the same degree the economic effectiveness of bird growing and quality of carcase and meat in the two examined strains of broiler chickens.