Tyre pressures change by 1 PSI for approx 4C change in temperature.
So a reduction from (say) 12C to 2C would account for a pressure change of 3/4 PSI.
Most handbooks say check tyre pressures when cold. Driving creates tyre movement, friction creates heat. A temperature increase of 20-25C after driving a few miles from cold is likely.
Because of the thermal mass of the tyre and wheel, the tyres do not immediately cool down - it may take 30 minutes.
I have always thought it more important for the tyre pressures across axles to be consistent even if the pressure varies by 1/2/3 PSI from what is recommended.
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