From the Intergovernmental Panel on Climate Change (IPCC) an expected air temperature increase between 2.5^oC and 3.5^oC is given for the 21st Century in Central Europe. At the local level (Saxony) also a change in precipitation regimes is expected. Slightly increasing winter and clearly decreasing summer precipitation lead to a reduction of the available ground water in the growing season. These changes lead to a change in the canopy climate, which affects the canopy itself. To investigate this feedback between the forest microclimate and canopy structure development is the major objective of this study. For that, simulations with the vegetation-atmosphere boundary layer model HIRVAC are used to quantify the variability of the forest climate. As input for the model investigations changing canopies for the actual state and for the IPCC scenarios B1 and A2 and for different age categories from the forest growth simulator BALANCE were used. The results show very well the interaction between changing external climate conditions, a variable stand structure, and the variability of the forest microclimate. With the assumption the mean summer temperature will increase, and the summer precipitation will reduced in the future, an intensification of the temperature extremes in the canopy can be expected. But otherwise a maximum damping effect of crown temperature of a possible forest between 5.4^oC and 6.2^oC could be simulated with HIRVAC depending on the considered climate scenario. Therefore, the forest planning is a possible instrument to control the climate conditions of the forests in the future.