After Mark Darcy has read Bridget's diary and then leaves her flat and goes out in the snow, and then Bridget goes outside after him in her underwear you can not see either of them breathing or any one on the street either as you should if it is snowing and she is apparently freezing! This also happens just prior to this when she is outside with her friends about to go to Paris and Mark Darcy arrives, you can't see anyones breath, which is completely unrealistic when it is snowing!