The temperature outside directly affects your tire pressure. The hotter the temperature, the more likely a tire failure, which makes it even more important to use a pressure gauge to check your tires. As the temperature increases, the air in your tire expands slightly to make the PSI higher. Conversely, as the temperature decreases the air in the tire contracts resulting in lower PSI. Ten degrees of temperature can result in one pound of pressure change. The best way to check your tire PSI is to wait until it is cool outside and the truck has been parked for several hours, that way you read the bottom end of your tire’s range and don’t risk having an under inflated tire.