Even brand new tires with minimal wear and tear lose air constantly. Factors that can affect tire pressure
Hot or cold temperatures.
Towing or carrying added weight in your vehicle.
Most tire and vehicle manufacturers recommend checking your tire's pressure each month, as they can lose multiple pounds of pressure within that time from simple daily use.
In addition, it's important to check pressure as temperatures heat up. Tires react quickly to changes in temperature, and a rise in heat can cause rapid pressure loss.
Leaky valve systems, low leaking punctures, and other often hidden damage can also decrease air pressure—all the more reason to check your tires regularly.