The temperature dependence of the dipole polarizability α(λ,T) of free atoms and molecules is determined by precise measurements of the refractive indexnof gases in the extended temperature range between 300 K and 1100 K for wavelength λ = 632·99 nm, using a specially constructed Michelson twin interferometer. α of the noble gases is observed to be independent ofT. α of the molecular gases H2, N2, O2, and CH4increases with increasing temperature by an amount of approximately 1 per cent per 1000 K. These results are in excellent agreement with theoretical predictions. They will be compared to previously measured temperature dependent polarizabilities.