Mostly cloudy this morning, then becoming partly sunny. A chance of showers. A chance of thunderstorms this afternoon. Much warmer with highs in the mid 70s. Southwest winds around 5 mph. Chance of rain 50 percent.
XL means Extra Load range which indicates the tire has a higher Load Index and Maximum Inflation Pressure (usually 51 psi instead of 44 psi) than a Standard Load range tire of the same size.
Second, a tire on a pickup can be an XL, but if a larger SL tire was desired, it could be used if it had the same or more load carrying capacity. It used to be fairly common for 1/2 ton pickups to come with XL tires, but the trend is towards larger, but SL tires.