Generally all diesel motors have a cold start advance feature, that will a) allow the engine to start when it's been left overnight in the cold, and b) stop the car bellowing white smoke out constantly until it is warm.
This will continue to function until such time as the engine temp sensor reads it is up to temperature then it will click back into the normal timing pattern. Like has been mentioned, with nights getting colder again, this will be more noticable now.
HTH.