Final answer:
The riddle describes an event that is initially scary but ends up being sweet, occurring at night to avoid heat. The answer to the riddle is Halloween, characterized by costumes that frighten and the sweet tradition of trick-or-treating.
Step-by-step explanation:
The riddle you've asked about seems to describe something that is initially scary but ends up being enjoyable and often occurs at night, likely to avoid the heat of the day. Let's consider what events or occasions fit this description. A common event that causes a 'huge fright' but is ultimately 'sweet' and celebrated mostly at night is Halloween. On Halloween, people often dress up in frightening costumes to scare each other, but the event is also associated with sweetness due to the tradition of trick-or-treating, where children receive candy. Hence, the answer to your riddle is Halloween.