Air temperature is a useful thermal index in thermally simple laboratory conditions but is inadequate when considering heat exchange in natural environments. Operative temperature more appropriately describes the effective temperature experienced by a free-ranging animal.
Parker, K. L., Gillingham, M. P.. 1986. Estimating Thermal Environments for Mule Deer (Odocoileus hemionus hemionus). Ministry of Environment. Wildlife Habitat Research Report. WHR-24