megnrose
Unreserved apologies if this is/was a genuine query
Assuming all other things equal - i.e. QNH and humidity - colder air (than ISA) will cause your altimeter to over-read and and warmer air (than ISA) will cause your altimeter to under-read.
Imagine you have a 2500' tape measure dangling from the aircraft.
Imagine also that you are at an
indicated 2500' on the altimeter.
On a cold (colder than ISA) day, the tape measure will read less than 2500'
On a hot (warmer than ISA) day, the tape measure won't be long enough
