Purpose of this study was to develop an early warning system for heat stress in cattle. For this purpose, total of 8 lactating cattle (4 Holstein of which 2 high and 2 low producing, 4 Brown Swiss of which 2 high and 2 low producing) which were raised at Dalaman branch of Agricultural Enterprises Directorate of Turkey were used. Before starting the experiment, adjustment time was given to the cattle to get used to human presence. After animals were accustomed to the human presence, researcher positioned herself in a shaded area where cattle came for shade seeking and skin temperature of cattle was read by infrared thermometer and also rectal temperature was read by using rectal probe. Temperature readings were taken at 10:00, 13:00 and 16:00. Study started on July 16 and lasted until August 16 when most of the heat stress is observed. Panting score of the animals were also recorded. Results showed that panting score increased as skin surface temperature increased. Rectal temperature also increased with panting score. Holstein cattle tended to have higher panting score than Brown Swiss cattle. Results showed that measuring skin surface temperature of cattle by infrared thermometer and observing panting scores could be used to early warn heat stress in cattle.