SUNSET WEDNESDAY, OCTOBER 19: The joyous week of Sukkot has drawn to a close for Jews today, and tonight, a new holiday begins: Shemini Atzeret. Shemini Atzeret may seem like the final day of Sukkot, since its name means “the assembly of the eight (day),” however, this is not technically true, since tonight begins a separate holiday. Rabbinic teaching indicates that the two holidays relate this way: Throughout Sukkot, G_d the Creator hosts Jews as his visitors, but when the time arrives for His visitors to leave, the Creator is enjoying His company so much that He asks them to stay one more day. In Israel, Shemini Atzeret is combined with another holiday, Simchat Torah; outside of Israel, Simchat Torah falls on the day following Shemini Atzeret. (Check out My Jewish Learning for a quiz, themes for today and more.)
After having eaten meals in their traditional outdoor shelters known as sukkahs—and, if possible, sleeping in them—Jews “wean” themselves from the sukkah today, spending a limited amount of time there. (Judaism 101 has more.) Work is still not permitted, and since there will be no dwelling in the sukkah tomorrow—and, therefore, no direct consequence of inclement weather—Jews begin to pray for rain. Rabbinic tradition has it that the world is judged for water for the upcoming year on Shemini Atzeret. (Read more articles for study at Chabad.org.)
Interested in how someone of the current era might delve deeper into the weeklong holiday of just-passed Sukkot? Check out an article in Jewish Weekly, in which the author takes time on Shemini Atzeret to compare Burning Man and Sukkot. The author refers to Shemini Atzeret as a day of rest—something of a day of recovery from weeklong party of Sukkot.