When the car is idling at a red light, and there are popping sounds similar to air blasts or backfires, what's happening?

Thermal expansion and contraction of the exhaust pipe.

I heard a loud bang from the back today. Not sure if it's the exhaust making noise. It might be due to the weather; never experienced this before, but it's gotten colder now.

There are a few popping sounds coming from the left rear side, and I still haven't figured out the cause.

Did you fill up at the small gas station?

Is there knocking?

Try a different gas station when refueling.