The HIS makes accurate radiometric measurements (absolute error <1K) with a reproducibility of 0.1K (a detailed description of the instrument can be found in Revercomb et. al. 1988), observing the upwelling radiance at sufficiently high resolution to identify individual absorption lines. This unique capability has resulted in the HIS measurements playing a central role in verifying and improving clear-sky line-by-line radiative transfer models. The HIS data, in conjunction with other observations made during these experiments provides a unique and important data set for clouds retrieval studies. HIS observations have been extensively used to develop methods of retrieving atmospheric temperature and moisture profiles and cloud properties. This paper will summarize that work and compare observations of cloud properties from the different FIRE experiments.