Determination of the maximum temperature in spatially non-uniform media by absorption spectroscopy with diode lasers is nontrivial problem. When thermodynamic equilibrium (TDE) is fulfilled the temperature of a uniform media is defined by fitting the experimental line profiles with the ones simulated basing on the spectroscopic data bases. In this simple case, two frequency-tunable diode lasers operating in the range of two strong lines with different energies of the lower levels are sufficient. However, in an inhomogeneous environment, the shape of the absorption line of the test molecule is resultant along the entire sensing path, which increases the number of parameters necessary to characterize the object. This leads to an increase in the number of detected lines (the number of diode lasers), an increase in the cost of the system, and a complication of the algorithm for processing experimental spectra. The article considers the case, which is important for the diagnosis of hot media, when it is necessary to determine not the exact profile of the temperature distribution, but only its maximum value. A minimum set of absorption lines has been determined, which can be used to estimate the maximum temperature under the assumption of its trapezoidal distribution in the medium along the sensing line. Combinations of four lines were found to solve the problem, and the accuracy of the maximum temperature estimate was evaluated. To determine the integral intensity of absorption lines in an inhomogeneous medium, a method is proposed for fitting the shape of the line with two Voigt profiles. It is shown that in the case of recording the minimum temperature at the boundary of the hot zone using commercial thermocouples, it is possible to use only three absorption lines. In this case, however, the error in determining the maximum temperature increases by about 4 times compared to the registrations of the four lines. Keywords: absorption spectroscopy, diagnostic of hot zones, non-uniform spatial distribution, fitting of absorption lines profiles.