

In 1994, Neville received a Howler from his grandmother, after he supposedly misplaced his password list enabling Sirius Black to enter Gryffindor Tower. In 1992, Ron Weasley received a Howler from his mother after he stole his father's Flying Ford Anglia. Neville Longbottom mentioned receiving at least one howler from his grandmother before 1992. The Lovebird to Love Note Transfiguration spell created a note that would verbally convey its message in a manner similar to a Howler, though at a significantly quieter volume. As such, a Howler would convey the displeasure of its author/sender even if left unopened, for it would shower the recipient with insults and cursing upon exploding into flames.

The purpose of the Howler was to deliver a message expressing anger or great displeasure in a manner which standard writing could not adequately convey. Once the message had been received, the envelope burst into flames, leaving only ashes. This mechanism ensured that the recipient would open the Howler, even though he or she knew that it contained an unpleasantly loud message. The physical temperature of the Howler would begin to rapidly increase upon delivery, and it would explode if left unopened for too long.
