Please feel encouraged to send prompts

Sometimes John had to remind himself that Sherlock was smart.

I mean, he knew he had a brilliant flat-mate. But…well. Sherlock could quote the entirety of Ode to a Nightingale but was rather naïve about what exactly a nightingale was; he had the alleys of London displayed like a map inside his head but was increasingly confused by the signs of any other city.

And John quickly learned that, while Sherlock could explain the scientific complexities of heat and cold, he wasn't skilled in applying such knowledge.

This was evident when John came home one late wintry evening to find Sherlock cross-legged on the floor of their sitting room, hunched over case files and test tubes, their thermostat showing -1C.

"Sherlock!" John adjusted the knob and ducked down near the detective, who hadn't looked up from his papers. He felt his forehead. "Okay, you git. Come here."

Sherlock finally registered his presence as he felt himself being lifted onto the couch. "John! Do you mind? I'm trying to figure out—"

"It's freezing in here, Sherlock—literally. Your skin is ice." He dumped the detective on the couch and piled several blankets atop him, turning to start the kettle. "What's the matter with you?

Wait… Nooooo…" John returned as Sherlock threw aside the blankets and tried to return to his papers. "Hey! I said no. You're shivering; goodness, your lips are purple."

Sherlock groaned as he was returned to the couch. "I must have bumped the thermostat when I was moving my equipment from the kitchen. This is a high-profile case, John. Did you know that in the sixteenth century—"

"Shush." John grabbed two cups of tea and wedged Sherlock between himself and the edge of the couch. "Here, drink. I'm going to come home one day and find you frozen solid. Why didn't you fix it?"

Sherlock shrugged, but it was hard to tell since his whole body was shaking. "I was focused on the case. As I was saying, there were these astronomers in the fifteen hundreds who thought it might be a good idea to—"

"You didn't think to put on your coat? Grab a blanket? Don't tell me you couldn't tell!"

Sherlock held the tea close to his chest and nuzzled his fingertips into John's jumper; the doctor yelped but let them stay put. "Well I didn't until you mentioned it. Thanks for that."

John sighed. "Sherlock. You know what a coat is for, don't you? You wear one enough on normal days."

"Yes." Sherlock watched his breath come out of his mouth in a white mist and disappear upwards. "It's simply not a priority. My hard-drive—"

"Can't function in extremes. Just like everyone else." John let Sherlock curl tight and close, his polyester feet finding warmth in his hipbone. "Add this as essential, alright?"

"Mmmm." Sherlock nodded and let his head fall against the doctor's shoulder. "Don't act like you're teaching me a vital lesson; I'm fully aware of how to…stay…" he started, voice lazy and low, until his eyes fluttered shut and breath deepened.

John sighed and leaned back into him. "I can't be your only source of heat," he said, but fell asleep himself.