"steamy" A/C

[jagdavey]

On one occasion last year, on a very hot summer day approachning over 30 degrees celcius, & on a long run from Germany back to the UK, after turning the A/C on again after a break, "Smoke", which I assume was steam or condensation was blown through the vents. After reaching Essex & taking the car to grange motors, brentwood for a quick check-up, they said there wasn't any problem. The same problem happened again last week on another very hot day. What could this be??