If it rains during Sukkot, we don't have to sit in the sukkah, correct? So why have I seen people who continue to sit in the sukkah even when it is pouring?

Answer:

Sitting in the sukkah is the only mitzvah that, if you're bothered by it, you're exempt. Usually, even when a mitzvah is hard, you have to do it. Like fasting on Yom Kippur, when only those who must eat for medical purposes may do so. Most people find not eating or drinking for 25 hours quite uncomfortable, but we still have to do it. And yet, if sitting in the sukkah bothers you, like in wet weather, you can leave and eat inside the house.

Nevertheless, many people refuse to eat outside of the sukkah, no matter how bad the weather, because they would be more bothered by eating inside a dry home than outside in a leaking sukkah. When you understand what the sukkah is, you'll see why.

The sukkah is a holy space. You are sitting in a divine abode, under the heavens, with the stars shining down on you, surrounded by angels and the souls of our forefathers. Our sages teach that we are only worthy enough to enter the sukkah after Yom Kippur, when our souls have been cleansed and we are at our spiritual peak. And the mystics explain that while the sukkah may look like a derelict hut cobbled together from wood and branches, in truth it is a made from the holy names of G‑d.

The weather may be a little unpleasant, it may be a little squashy in there, and your palm allergy may be flaring up...but the inner serenity, the love and feeling of connection with those around you, the sense of being embraced by G‑d—all that should override any physical discomfort. If you're still not enjoying the sukkah, then you're not really in the sukkah in the first place, and you can go inside. But if you know what your missing, you won't want to leave.

There are moments when we are called upon to transcend the material world. Sitting in the sukkah is one of those moments. A little rain, or even a lot, can't stop that.