The problem of hydrodynamic motions of saturated wet air under condition of interphase equilibrium of steam and steam condensate is considered. The separation and absorption of concealed heat of stream condensation leads to modification of usual hydrodynamics modes, which respond to sound waves and convective instability. The dependence of critical Reley number of convective instability and absorption of sound wave due to heat conductivity from thermodynamics parameters of wet air is studied. The results of investigation of “wet convection” are used for estimation of intensively of convective turbulence in powerful cloudy systems.