Maximum temperature changes are one of the most important factors in plant growth and heat wave as one of the most harmful climatic hazards. The purpose of this study was to predict the maximum temperature and heat waves with the plant ecosystem approach in Sanandaj and Kermanshah from 2020 to 2050. For this purpose, the maximum daily temperature data were obtained from the Meteorological Organization from 1961-2005 and were simulated using SDSM software and CanESM2 model and under the most appropriate RCP scenario for the next 31 years was predicted. Then, by programming in MATLAB software and applying the Fumiaki index on the predicted maximum temperature data, the heat waves of these cities from 2020 to 2050 were identified and divided into two categories: long-term heat waves and short-term heat waves. According to the results, RCP4.5 and Rcp 8.5 scenarios were selected as the least error scenarios to predict the maximum temperature of Sanandaj and Kermanshah, respectively. According to the findings, the cities of Sanandaj and Kermanshah (2020-2050) will not experience long-term waves and the maximum duration of heat waves in Sanandaj will be 5 days and in Kermanshah will be 4 days and short-term heat waves of 2 days will be most frequent. Also, the trend of maximum temperature in both cities will increase and the trend of heat waves during the forecast period in Sanandaj will increase and in Kermanshah will decrease slightly. The highest frequency of heat waves occurred in these cities, often in the cold months.