We have noted a seasonal bias in the Moderate Resolution Imaging Spectroradiometer (MODIS) 4µm Thermal Infrared channels, both in observed data and in modeled Top Of Atmosphere Brightness Temperatures. The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Visible/IR Imager/Radiometer Suite (VIIRS) instrument employs detectors with similar spectral response functions. This study demonstrates several possible causes of this seasonal bias, and a solution for improved 4ìm Sea Surface Temperature (SST) retrievals. We conclude that seasonal and meridional trends in error may be correctable in both VIIRS and MODIS 4µm SST products.