The aim of this study was to assess the influence of summer temperatures on the milk content and technological properties for three different cow breeds. The experiment took place between June and August 2015. We observed 18 dairy cows, kept in identical conditions. We used cows of 3 breeds: Czech Fleckvieh (C), Holstein (H) and Ayrshire (A). Samples were taken weekly. The analyzed parameters were: total yield per observed period, milk content, density, active and titrable acidity, rennet coagulation time (RCT) and curd class quality. Average daily yield was 22.8 (A), 28.1 (H) and 24.4 (C) liters. All cows were at the same lactation (2nd). All breeds showed an increase (from 12.74% to 12.24%) in dry matter. Titrable acidity was significantly (P < 0.05) increasing and active acidity was decreasing for all three breeds. When it comes to technological properties Czech Fleckvieh and Holstein showed a decrease in RCT and curd quality, and Ayrshire showed an increase in both RCT and curd quality. This can point to the fact that, though these three breeds are different, some characteristics (dry matter, titrable and active acidity) of their production are affected by the high summer temperatures. RCT values indicate that Czech Fleckvieh is more adaptable to high temperatures.