We describe atmospheric temperature inversions and height-resolved water vapor fields over the wintertime subtropical northeastern Pacific Ocean in observations by the satellite-borne Atmospheric Infrared Sounder (AIRS) experiment. A comparison with model analyses shows good agreement in temperature. Water vapor comparisons with operational radiosondes at four sites in California and Hawaii during December 2002--January 2003 have low biases in the 1000--700 and 700--500 hPa layers. Maps of inversion frequency, and, water vapor at 1000--700 and 700--500 hPa over the subtropical northeast Pacific during 1--16 January 2003--when high pressure and clear conditions prevail--show inversions occurring at a local minimum in water vapor at 1000--700 hPa. Water vapor at 700--500 hPa has a broad minimum extending from Baja California to Hawaii, with inversions found on its eastern half. These observations illustrate the potential of the AIRS data for describing a climatology of temperature and water vapor in subtropical oceanic regions.