There's not enough information in this post to really know. But let's say you were stopped and autostop was engaged. Your A/C compressor is a dual mode one. Meaning, when the engine is running the A/C is mechanically run. And when the autostop is engaged, the A/C is in electric mode (running off the hybrid batteries). So yeah, if you're in autostop, sitting in traffic, with the A/C on, then the battery meter will deplete faster. Sometimes a lot faster. Once you get down to one bar (or maybe no bars, I don't remember) the car will restart and begin to recharge your hybrid batteries.
If this sounds like what your car is doing, then yeah, it's normal. It's freakin' hot out there. Go ahead and leave that A/C on.
