949. Rain and Cold on Succos

135:9 One is exempt from dwelling in a succah when it rains to the extent that the rain would ruin the food - even if the food is not actually in the succah - or if he estimates that if this much rain had fallen in a room of his house then he would have gone to another room. In such a circumstance, he leaves the succah and goes in the house. If one started to eat in the succah and rain began to fall so he went in the house and started to eat there, or if rain was already falling and he started his meal in the house then the rain stopped, he finishes his meal in the house and is not required to return to the succah in the middle of the meal. Similarly, if the weather is cold so that one's food freezes in the succah, he is exempt from eating in the succah and he eats in the house. (All the more so he may go in the house if the cold makes him uncomfortable – Shaar HaTziyon 639:59.)

135:10 When it comes to sleeping in the succah, even light rain makes it uncomfortable and one may leave the succah. If one went in the house and lay down to sleep, after which the rain stopped, or if he initially lay down to sleep in the house because it was raining and then the rain stopped, we do not trouble him to return to the succah during the night. Instead, he should just sleep in the house until the morning. (If he has not yet laid down to sleep, he must return to the succah, though some authorities feel that once he has bothered to drag his pillows and blankets into the house, we do not trouble him to return to the succah – Mishnah Brurah 639:40.)