The fluctuating displacements of a laser beam crossing a strongly nonisothermal channel air flow have been measured in the range [10(4)-3.5 x 10(4)] of the Reynolds number based on the hydraulic diameter. The measured instantaneous displacements are useful data for testing direct numerical simulations of nonisothermal turbulent flows. It is shown that the variances of these displacements are related to two-point correlation functions of temperature and temperature spatial derivatives. A first approach developed here to predict the beam displacement variances is based on a four supplementary equation, near-wall, turbulence model. These variances are shown to be related to components of the dissipation rate epsilon(theta) of temperature fluctuations. A satisfactory agreement between measured and predicted displacement variances is obtained.