Of the mitzvot d'oraitha - biblically-mandated commandments - that are applicable in modern times, few are as widely ignored by otherwise religious Jews as is the requirement for men to sleep in the sukkah during the festival of Sukkot.
We all build sukkot, we all eat our meals in them unless it's raining, and many are careful to avoid even snacking outside the sukkah. But remark to someone about how well you slept the night before, and more often than not you'll elicit reactions of surprise, even discomfort.
"Oh, you sleep in the sukkah?" "Well, I kind of figure it's a mitzvah d'oraitha."
Often these are people who are very finicky about choosing their lulav and etrog and would rather order the fruit salad than risk an inferior hechsher.
It's not entirely clear when or why sukkah-sleeping fell out of common practice among Ashkenazim, though many halachic authorities consider it to be the essence of the mitzvah of sukkah, far more significant then eating there. Presumably the cold October climate in many northern countries, combined with dangers Jews often faced from the societies around then, were seen to constitute a "discomfort" exemption to sukkah-dwelling.
I certainly never slept in the sukkah when I was growing up. As far as I know, neither did my friends or their fathers - regardless of how religious they were in other respects.
With rare exceptions, this is a mitzvah I've only started observing since making aliyah. In Israel, neither the weather nor the neighbors are usually a concern this time of year. Sukkah-shluffing is clearly far more common here than overseas. Still, I wonder how many congregants in my synagogue sleep in their sukkahs. Not many, I suspect.
Even in chutz la'aretz, though, the mitigating circumstances do not necessarily still apply. Heating is safe and affordable, as is Thinsulate. Pogroms remain rare, especially in suburbia. What remains is the "weird factor" - who ever heard of sleeping in a sukkah in this day and age? - and the "bourgeois factor" - I don't mind a chilly picnic with bees for the mitzvah, but I'm not about sleep out in the cold with creepy noises!
The difference between eating in the sukkah and sleeping in it is like the difference between a picnic and a campout. There is a vast difference in the degree of exposure the elements, the sensation of vulerability, the awareness of one's dependence on God, and, in general, the ability to identify with the experiences of the Israelites in the desert, which Sukkot commemorates. They didn't have comfortable homes to move back to between meals.
If you have a sukkah, all you need to add is a folding bed, mattress, or good sleeping bag. You might want some mosquito repellent, or, if it's cold or noisy, earmuffs. Depending on how you sleep and when the sun rises, you might not even need an alarm clock.
This Wednesday night's forecast calls for a low of 56F and clear in New York City, 60F with scattered clouds in Los Angeles, 46F (brrr) and clear in Chicago. Even dreary London is expecting 53F (12C) and cloudy.
Personally, in Israel I'm looking forward to a balmy 77F (26C) and clear. Nyah!
I hope you join me. Clouds permitting, I guarantee you a beautiful full moon.
(Don't try this in Florida, though! Stay safe and dry!)