The dataset contains the results of the experiments perfomed with the Fast InfraRed Hygrometer (FIRH) at the Turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T) which are presented in the figures in the article "Contactless optical hygrometry in LACIS-T" submitted to Atmospheric Measurement Techniques.FIRH is an open-path optical sensor developed for high-resolution measurements of small-scale humidity fluctuations in turbulent atmospheric flows. The device employs open-path tunable diode laser absorption spectroscopy at the wavelengths near 1364.6896 nm...