Apologies in advance - I still have new car paranoia

Today, went for a small drive and went to get some fuel. On pulling out of the petrol station, the entire cabin filled with steam and it looked like it was coming from the air vents (behind the handbrake). Is this normal?
The car was fairly warm before I pulled in to get petrol and was left standing for about 10 minutes. The air con & heaters were on. Once the steam had cleared, the car seemed fine - all the temps were fine and she drove perfectly.
Is this just a 'quirk' of ownership?