Yup.
This is due to the fact that your car’s engine and interior will function far below the freezing point of water. The heat from your car helps keep it warmer than outside, and helps reduce the chance that water in a bottle will freeze (especially if you open and close your windows). However, without any insulation for protection, this weather instability can make your water very cold after only about 15 minutes. And because our mountainsides get more sunlight on average than other places like Montana or Oregon (due to lower elevation), these effects are accentuated even more over here.