A mobile device comprising a pressure sensor for collecting pressure data, a position-determining subsystem for generating location data including altitude data, and a processor operatively coupled to a memory to generate an atmospheric model based on the pressure data and the location data. In one implementation, the processor is configured to determine an Above Mean Sea Level (AMSL) altitude using a position-determining subsystem, determine a pressure altitude using the pressure sensor, calculate a difference between the pressure altitude and the AMSL altitude, and calculate a temperature at sea level based on the AMSL altitude and pressure altitude. In one implementation, the processor performs a linear regression on an equation AMSL altitude=offset+ScaleFactor*PressureAltitude to solve for the offset and the ScaleFactor, and then estimates the temperature at sea level as 1-ScaleFactor=(T−15)/3. The model may be used to estimate ambient air temperature or weather conditions.