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Heat tolerance is widely considered to become in the future a key trait in breeding wheat for increased yields and yield stability in many parts of the world. Success in breeding for heat tolerance is dependent on the efficiency of methods to expose breeding material to higher temperatures in key phenophases. A simple and not expensive approach, based on covering plants in the field with transparent cellophane paper, was tested during 2017 and 2018 at the National Agricultural Research & Development Institute Fundulea, Romania. The adopted system, described in this paper, increased the temperature under cover as compared with surrounding temperature in open air by +1.74 to +3.69 degrees C on general average, and by +5.55 to +11.83 degrees C for the average of daily maximum temperatures. As a result, the weight of 1000 kernels (TKW) was reduced by 9% on average over 15 cultivars and two years of testing, with large differences among the tested cultivars, with reductions ranging from less than 5% to more than 20%, on average over the two years. TKW reduction was significantly correlated with anthesis date (r=0.528* to 0.646**). Deviations from the regression describing the relationship between anthesis date and TKW reduction allowed the discrimination of the confounding effect of earliness on the performance of cultivars under increased temperatures stress. The classification of cultivars according to the deviations from the regression corresponded quite well to that expected based on previous information and observations.