Cold vs. hot tire pressure

I have a TPMS in my truck and was really surprised to see the magnitude of increases in pressure. I originally set my tires to 80 psi at ambient temps (about 70 degrees). After driving on the highway on an 80 degree day, I checked and found my rear tires were at 254 psi. It turns out that the TPMS only goes to 92 psi and after that the pressure reads at 254. I often go over the 92 psi limit on my rear tires. There is a lot less weight on the front tires and they are always under 90 psi. Actually now they are well under. I have the pressure set at 60 psi on the front tires and they end up at about 70 psi for highway driving.