Upcoming means happening soon. If you've always wanted a surprise party, you might drop hints to your friends about your upcoming birthday.
The adjective upcoming was first used in the 19th century to mean "rising," but its meaning changed to "forthcoming" or "imminent" by the mid-20th century. If you'll vote next month, you might talk about the upcoming election, and your little sister might be excited about your upcoming family trip to Disney World. Whenever you find yourself thinking of an event that's coming up, it's upcoming!