Once again, you can book fares for under $100, and you have just a few days to do it. The offer ends on Friday.
You can get low fares on domestic travel between 8/13/18 - 12/19/18.
You can book flights to and from Puerto Rico if you travel between 9/5/18- 12/5/18.
Check the Southwest Airlines website for specific restrictions.
Keep in mind that booking for flights during this promotion is nonrefundable. But if your travel is a sure thing, you might want to go for it.