A good rule of thumb is a one psi increase or decrease for every ten degree Fahrenheit change in temperature. This is why it's very important to check and adjust cold inflation pressures whenever the ambient conditions change significantly. If you inflate your tires to the recommended cold pressure when it's 80°F outside, then have a severe cold front come roaring through, you will find your tires severely underinflated. On the flip side, if you start out at 30°F and a big heat wave comes through, your tires will be overinflated. Either under or over can create safety issues.
It is perfectly normal for those TPMS readings to increase as the tires heat up during operation. Once again, verify with a known accurate gauge if you believe your system is giving you bogus readings. Having TPMS doesn't mean you can throw away your gauges, you still need to do old fashioned inflation checks and tire inspections.
Jerry