It wasn't something Jason noticed at first. The way he seemed to get colder much easier than before, or the way he seemed to be drawn to hot drinks every time he went to the café, where he used to prefer iced.
You noticed it before he did, truthfully. His body was always so... cool. You'd always have to bundle him up when he went out on a patrol, and you kept a heated blanket waiting for him when he got home. You always assumed it had something to do with his resurrection. Maybe his body temperature never regulated back to where it was supposed to be. His body temperature wasn't a topic the two of you had ever really discussed, but you both seemed to know without having to say anything.
Regardless, Jason would use this to his advantage on occasion. The two of you were in bed, cuddled up under a mountain of blankets to keep out the cold winter air. Jason wrapped his arms around you, and chuckled when you let out a squeak of discomfort and began trying to pull his hands off of you.
"Sorry, are my hands too cold, babe?" He asks in a low, playful tone. Jason always did this to you, and he knew you hated it.