The scattering of a one‐megacycle underwater ultrasonic beam by a radial cylindrical temperature gradient perpendicular to the beam is studied as a function of position and gradient strength. The gradient is produced by a vertical hot wire. The presence of free convection currents makes necessary time average study of both the temperature and scattering distributions. From these studies average temperature and scattering distributions are constructed, and it is found that a possible diffractive transition region exists between temperature gradients of 14.5 and 26.5°C/cm. In addition, there is evidence that a transition from wave to ray acoustics occurs between gradients of 26.5 to 36.5°C/cm.