The amount of polarisation can be understood as the extent of perfect alignment of the molecules of a dielectric with an external electric field. The more aligned the molecules are with the external magnetic field, the more is the polarisation and the more will be the dielectric constant.But with increase in temperature, the thermal agitation of the molecules or the randomness in their alignment with the field increases.Thus, we can say that increase in temperature results in reduced polarisation and reduced dielectric constant.