Modern experimental techniques like Background Oriented Schlieren or Infrared Thermography allow timeresolved measurements of 2D temperature fields. The remaining hydrodynamical quantities − velocity and pressure − are to be found from complete numerical simulation, which is verified by comparing the measured and simulated temperature fields. However, in some flows, involving physical effects, adequate boundary conditions or source terms in equations can be unknown. In such cases experimental temperature data can be used as input for velocity and pressure reconstruction based on the remaining part of the complete system of hydrodynamical equations. Two variants of velocity reconstruction are proposed. The first variant makes use of energy equation and optical flow or cross-correlation algorithm to derive velocity components from sequential temperature fields. The second presents incomplete numerical simulation, where experimental temperature fields are utilized to calculate buoyancy force. Pressure reconstruction is based on Poisson equation derived from momentum and continuity equations. All the proposed techniques are verified using simulated and real experimental data for convective plume over a horizontal heater in liquid and thermal structures at the surface of evaporating liquid. The possibility of reverse determination of temperature field from experimental velocity data obtained by Particle Image Velocimetry in natural convection flows is also discussed.