Abstract A database of temperature‐dependent hexagonal ice aggregate optical properties in the far‐infrared (FIR) spectrum is developed to support FIR missions, particularly the current Polar Radiant Energy in the Far InfraRed Experiment and the upcoming Far‐infrared‐Outgoing‐Radiation Understanding and Monitoring. Based on this data set, simulations of the brightness temperatures (BTs) in the 100–667 cm−1 FIR region are conducted for an anvil‐like ice cloud in a tropical atmosphere. The results show nonnegligible impact of ice cloud temperature on simulated BTs, which can be as large as 3 K due to the difference between fixed 160 or 270 K cloud temperature and the benchmark counterpart, varying in accordance with the ambient temperature profile for a cloud residing between 249.6 and 199.6 K. To enhance the accuracy of FIR radiative transfer modeling, it is recommended to incorporate temperature‐dependent optical properties of ice clouds.