The National Airborne Sounder Testbed - Interferometer (NAST-I) WHyMSIE dataset provides high spectral and spatial resolution passive infrared sounding observations. The NAST-I instrument provides observations of temperature, humidity, and cloud properties covering a spectral range of 3.5-16 microns. These data were collected during the Westcoast and Heartland Hyperspectral Microwave Sensor Intensive Experiment (WHyMSIE) field campaign. WHyMSIE aimed to capture a wide variety of thermodynamic, moisture, and planetary boundary layer regimes across a variety of surface types. Comparing observations from NAST-I, other instruments, and with in situ observations of temperature and humidity will allow for scientific advancement of remote-sensing techniques into the hyperspectral microwave era and improved understanding of the planetary boundary layer at different measurement scales. These data are available in netCDF-3 format from October 22, 2024 through November 13, 2024.