CallmeJB is right!
Simple calculation for temp corrections is 4 feet/degree off standard/1000 ft. Say there is a step down fix of 5000' on an ILS to sea level( like LAX)because traffic to a different airport gets vectored at 4000' at that point. Say the actual temperature is 30, calculation is then that the aircraft on the ILS at 15 miles out where he is at a actual height of 5000 would be at an indicated altitude of 5000-(5 times 4 times 15=)300= 4700 if he where to follow the glideslope. There would be a loss of separation with the aircraft below being vectored at 4000 of 300 feet.
If you don't believe this effect look at a regular ILS approach. Usually there is an altitude check around 4 miles(outer marker/dme fix etc) you should be around 1200 ft on a standard day! On a colder day, say 0 degrees your altimeter will indicate 1.2 times 4 times 15= higher, in this case 1272, if it is warmer it should read 1128