Oh come on! Okay, let's swing this dead cat.....
So how cold is cold? Certainly I think less than 100*C qualifies?:
Snap-On:
"The compression test consists of measuring cylinder
pressure at cranking speed. Use the test results to
determine the condition of pistons, rings, valves, and
gaskets. It is good procedure to perform a compression
test prior to performing a tune-up.
Certain conditions affect the compression readings.
These conditions must be understood before testing.
• If the engine turns slowly, gauge readings are lower.
Be sure battery and starter system are in good
condition. The engine must turn at the same speed for
all cylinders.
• Open throttle plates and choke plate to allow the
engine to breathe. Be sure air is not restricted from
entering into the cylinders.
• Temperature of the engine must be at operating
temperature. A cold engine does not insure proper
tolerances, lubrication at the rings, or proper ring
seating.
Engines with aluminum heads require special care to
prevent stripping the spark plug threads. Since
aluminum cylinder threads are less likely to strip
when the engine is cold, it is good procedure to
prepare for a compression test by loosening and
retightening the spark plugs when the engine is cold.
3 Before removing spark plugs, always clean dirt
from around the plugs by directing an air nozzle
at the base of the plug. This insures proper
seating of the compression adaptor and the new
spark plugs. Apply a drop of oil to threads and
hand tighten when installing and removing
compression adaptors.
• Remove all spark plugs from the engine. Failure to
remove all spark plugs could affect the test results."
http://buy1.snapon.com/products/diagnostics/usermanual/zmt308l.pdf
