DA = PA plus or minus 120T where T is the difference between the ICAO standard atmosphere at a given PA and the real temperature.
Covert your elevation to PA by adding or subtracting 30' for every millibar your QFE differs from 1013. Then compare actual OAT with what it should be at that PA and multiply the difference between the two by 120 which will give you DA.
The warmer the air the higher the DA, the lower the pressure the higher the DA.
High DA makes your aircraft perform worse as the air is less dense.