You know the increasing popularity of Yennefer And Jaskier Share A Bed At Kaer Morhen Because "Its Cold" has got me thinking. Some fics have touched on how Yen doesnt have to do this to stay warm, especially if she had to go thru a recovery period and thats over now. So i guess they could keep up the "its cold and we're just weak humans" if Yen says that using magic to stay warm all night is a unnecessary drain (whether or not thats true...)
But then you have Ciri. Geralt hears Yen and Jaskier, two people who hate each other, are sharing a bed every night because its that cold at night, and immediately thinks how Ciri has been sleeping alone in the cold for a month(?) now.
So the truth about Ciri can make or break yennskier's flimsy excuse. Either Ciri is relatively fine and the excuse is bogus (unless they blame it on her youth or her not 100% human heritage, which are weak arguments, or the rooms with rats really are that much warmer), or she's been freezing every night and hasnt told anyone because she's been trying to look tough