From my SmarTire manual as Ray has noted previously.
A tire is considered to be “cold” when its temperature is 65°F
(18°C). The inflation values provided by vehicle manufacturers
(found in the vehicle’s owners manual and usually on the door
jam or in the glove box) are called ‘Cold Inflation Pressures’ (CIP)
because they represent the correct amount of pressure a tire
should be inflated to when it is “cold”. The reason that tires have
cold inflation pressures set at 65°F is because a tire’s pressure
will change relative to its temperature.

A tire inflated to a CIP of 105 PSI at 65°F will increase in pressure
to 125 PSI at 152°F and decrease in pressure to 97 PSI at 32°F.
As such, on days when the ambient temperature is higher than
65°F, the cold inflation pressure of a tire should be higher than
the value specified by the vehicle manufacturer. The opposite
applies for days when the ambient temperature is less than 65°F.