Many variables.  Our TST system recommends a warning at 20% over ambient pressure.  Front axle, 70psi cold/ambient high alarm set for 84, rear duals 80psi, alarm set for 96psi.
Normally the rears will go from 80 to 92 to 94 at about 70degree temps, but one trip, all four hit pressures of 98 to 102 in air temp over 100degrees.  As long as all tires are within 5 or 6 lbs of each other and tpms temps similar I don't worry about it.
Beverley and Ken