Chapter 1: Thor
As much as it pains him to admit it, rain reminds him of his lost brother. If asked about the comparison, he would explain that Loki always shined the brightest in the gloom of a rainy day. His younger brother became the sun on those days, radiating a warmth that never existed on any other day. He had a joy that couldn't be rivaled. And Thor coveted those days because he wanted nothing more for his brother than to see him so happy.
Without Loki, rainy days began to weigh heavily on his heart. He would think too long on things that used to be, or could have been. He found himself slowly drifting into an uncharacteristic sadness on the days when the sky was gray and crying. Sometimes, he even found himself crying with it.
Until he met Jane.
With Jane Foster, Thor found his light again because Jane loved rainy days just as much as Loki had. She glowed just as brightly and smiled even more. On rainy days, Jane threw herself into her research with more vigor than Thor had seen in Volstagg, throwing his-self into a feast. On rainy days, Jane Foster was simply more alive. And that was the exact same way Loki had been in their youth.
It was those days that Thor chose to spend with Jane more than any other. No matter the date, if it was raining, Thor was with Jane. Most days, that meant sitting on a stool in Jane's lab, watching her work. Often, mellow music played softly, only just loud enough to be heard over the gentle patter of the rain.
When the rain was too hard and interfered with Jane's work, they would sit, curled up on a wide suede sofa, and listen to the same mellow music. They would whisper stories about their childhoods, laugh gently together. And Thor, whose only volume on any normal day was sonic boom, was quiet and light as the flutter of a butterfly's wings. Because he couldn't, for the life of him, bear to disrupt the peace that was between them. He wouldn't distract from her vitality.
And so they lay together, murmuring stories in the gray light. And for all the world, Thor could not think of one thing that filled him with more joy than lying on that sofa on those tranquil days.
Chapter 2: Steve
It was nearly five hundred miles from the Avengers' temporary headquarters in Stark Tower to the family cemetery where Agent Margaret Carter was buried. At first, he made the trip. Every rainy day he got, Steve Rogers mounted his motorcycle and drove the seven hours to visit her. And, at first, no one minded. But, after a while, Fury began to complain. And when Fury complains, you correct the problem.
So, for months, Steve stopped making his rainy day pilgrimage to Virginia. And for months, Steve was miserable. Instead to riding all day, he ran. He ran laps around Central Park. For days.
After six months of Steve's depression, Tony, Clint, Thor, and Bruce put their heads and resources together to build a miniature memorial to Peggy and Bucky in the greenhouse. Tony even installed an irrigation system in the ceiling that JARVIS synced to the weather patterns. Thus, when it rained outside, it rained inside.
Steve spent many rainy days in the greenhouse, getting soaked to the bone and talking to his best friend and the love of his life. He sat for hours, until water filled his shoes and his hands wrinkled. Many times, it was only the sun falling beneath the horizon that drove him up to his rooms.
No one bothered Steve on those days. And he always walked away from it happier.
Chapter 3: Tony
Truth be told, rainy days don't affect Tony much. Truth be told, he usually sleeps through them. Either he can't or won't lift a finger for work and just sleeps.
It's when rainy days fade into stormy nights that Tony's bothered. It's those nights, when thunder claps in the dark and lightning flashes across the jet-black sky, when Tony wants...no, needs company. Whether than meant someone he knew or some ditsy girl from some random bar didn't matter. He always found someone.
On occasion, that someone was Pepper. She'd curl up on one of the many black leather sofas with him and they'd sit in silence for hours. She'd run her fingers through his hair and comment on how long it was getting. He'd huff out a laugh then not say a word, just enjoying the company. She was so much more than his assistant. She was more than his friend. He didn't know what to call her, but she was a blessing to him.
Sometimes the someone was Steve. They'd sit and chat, muttering in the dark. Lightning flashed across both of their faces, both of them haunted by ghosts of their pasts. They didn't talk much beyond idle chat. They didn't need to. They each knew what had happened to the other. They didn't need to ask, to revisit it. So they sat. One would lay down, head resting near the other, and they'd sleep. And that was fine. They didn't question it. They didn't care. So long as they didn't have to be alone.
Most of the time, Tony would venture up to the labs and would find Bruce. The doctor always had music on of some sort, taking advantage of the stereo systems Tony had installed everywhere. As if knowing he'd come, when Tony would enter Bruce would grunt a greeting, never looking up from his work. With Bruce, Tony didn't need to talk. There was no chat, no banter, just comfortable silence. Bruce would work and Tony would watch. Sometimes he'd thumb through Bruce's notes, ever curious as to what the doctor was working on.
Some nights, when he was feeling especially low, Tony Stark would have his AI call down to the prison cells. Within seconds, a whirl of green smoke would deposit a serene Norse god, kneeling, in the center of the room. He would rise, jet black hair falling around his pale face, green eyes glowing with magic. He would silently make his way to fold himself onto the couch with the shorter man, and would lay with his head resting on Tony's knee.
These two lost and broken men would talk for hours, taking turns asking questions. They'd talk about their past lives, parents, past lovers, old friends. Tony would inquire about the inner working of the universe. Loki would ask about the inner workings of Tony. They talked about Asgard and New York, Odin and Howard, and even the branches of Yggdrasil. The well of topics they explored never ran dry.
And Tony liked it that way. It distracted him from the demons of that particular day. He even began to look forward to those nights on his couch with the God's head in his lap. After months of calling the god to him, it became a habit of Loki's to appear on Tony's couch during storms sometimes the mortal would be there and sometimes not. But he always waited. And Tony always sat with him, even if they didn't feel like talking. Because it was better to have someone there to chase away the nightmares than to sleep through them alone.
Chapter 4: Bruce
Let it not be said that Bruce Banner is afraid of nothing. He is, in fact, afraid of a great many things. However, rain is not one of those great many things. Therefore, Bruce Banner enjoys taking walks on days when everyone else is rushing about to get in out of the wet.
Something about the constant rhythm of the droplets pattering on the concrete and asphalt, Bruce found soothing. He found it so soothing, in fact, that listening to it and the sounds of the cars rushing by in the busy New York streets was one time when Bruce could honestly say that he wasn't angry. But that did frighten him. And, at that point, he fled back to his lab and immersed himself in his work.
Usually it was some odd experiment that he excused himself with. Never, of course, would be admit that he'd been scared in from the rain by being calm. So, he examined his blood under the microscope, again. He poked and prodded at it, sighing in dismay when it would go a familiar green hue and break yet another slide. He jotted down notes on the time it took from when he drew it, or how calm he was when he took the blood. He took the temperature and humidity of the room to see if the transformation took longer in the cold, or in humid weather. Anything that could point him in the direction of repressing the other guy more.
When rainy days faded and gave way to stormy nights, Bruce found his lab home to his teammate and friend, Tony Stark. He didn't know what demons brought Tony to the labs instead of to his bed or workshop, and Bruce didn't want to know. The other man sought companionship. And it just so happened that his companionship didn't require Bruce to take any attention off his work. For that, Bruce couldn't tell if he was grateful or remorseful. Because he enjoyed talking with Tony in the light of the day. Sharing ideas, or even explaining the finer points of a theory to the rest of the team with him. It was amazing to him what the mind of Tony Stark brought forth every day.
However, on those nights, Tony was different. He was quiet. He was reflective. It was on those nights when the man with a wit to match the God of Lies was absolutely silent. He examined Bruce's notes, surely seeing that all of his tests were in vain, but never saying a word. And for that, Bruce was grateful. After all, he didn't need Tony Stark to tell him what he already knew.
There was no keeping the Hulk down. No repressing it, no getting rid of it. He was a part of Bruce the same as Bruce was a part of himself. And that's what frightened Bruce Banner most of all.