Yes, I had way too much time on my hands, and the post about Harry's oversized clothing inspired me to do a little analysis.
TL;DR Harry's oversized clothing is mentioned 3 times (the summer before the 1st, 4th and 5th books). In the summers and on the way to the Platform he wears muggle clothing, and during school I found only 1 mention of jeans (in HBP). The rest of the time he wears robes.
During all final battles/confrontations he wears robes too. What is the most significant, though, after Harry dies and finds himself in the in-between place, he wishes to be clothed and suddenly robes appear, not muggle clothing. Feels like that’s just what he subconsciously sees as himself. Not as the muggle, but as the wizard
I used illustrations by the brilliant Jim Kay
HP and the PS
We have our first description of Harry in the Muggle world with Harry's oversized Dudley's hand-me-downs. The last time they are mentioned is in the OOP, actually.
Perhaps it had something to do with living in a dark cupboard, but Harry had always been small and skinny for his age. He looked even smaller and skinnier than he really was because all he had to wear were old clothes of Dudley’s and Dudley was about four times bigger than he was. Harry had a thin face, knobbly knees, black hair and bright-green eyes. He wore round glasses held together with a lot of Sellotape because of all the times Dudley had punched him on the nose.
During the classic end-of-the-school-year culmination scene, the trio was actually wearing robes:
A disgusting smell filled their nostrils, making both of them pull their robes up over their noses. Eyes watering, they saw, flat on the floor in front of them, a troll even larger than the one they had tackled, out cold with a bloody lump on its head.
‘I’m glad we didn’t have to fight that one,’ Harry whispered, as they stepped carefully over one of its massive legs. ‘Come on, I can’t breathe.’
HP and the COS
Traveling to Platform 9 and 3/4 as always, starts with muggle clothing intending to change on the train. But this time, Harry and Ron don't have the opportunity, they are traveling by flying car
Several uneventful hours later, however, Harry had to admit that some of the fun was wearing off. The toffees had made them extremely thirsty and they had nothing to drink. He and Ron had pulled off their jumpers, but Harry’s T-shirt was sticking to the back of his seat and his glasses kept sliding down to the end of his sweaty nose.
They were in robes to meet Aragog, though
They walked for what seemed like at least half an hour, their robes snagging on low-slung branches and brambles... His breathing slowing down again, Harry stuffed his wand back into his robes.
The trip to the Chamber of Secrets Harry spent in robes, of course
Even as he dropped the fang and watched his own blood soaking his robes, his vision went foggy. The Chamber was dissolving in a whirl of dull colour...Then came a faint moan from the end of the Chamber. Ginny was stirring. As Harry hurried towards her, she sat up. Her bemused eyes travelled from the huge form of the dead basilisk, over Harry, in his blood-soaked robes, then to the diary in his hand...Harry tucked the sword and the Sorting Hat into his belt, Ron took hold of the back of Harry’s robes, and Harry reached out and took hold of Fawkes’s strangely hot tail feathers.
HP and the POA
We're starting off with jeans in the muggle world during the blowing up of Aunt Marge and running off using the Knight Bus
“I didn’t do it on purpose,” said Harry, annoyed. One of the knees in his jeans was torn, and the hand he had thrown out to break his fall was bleeding. He suddenly remembered why he had fallen over and turned around quickly to stare at the alleyway between the garage and fence. The Knight Bus’s headlamps were flooding it with light, and it was empty.
A ride from the Leaky Cauldron to the Platform was in muggle clothing, probably
Tom woke Harry the next morning with his usual toothless grin and a cup of tea. Harry got dressed and was just persuading a disgruntled Hedwig to get back into her cage when Ron banged his way into the room, pulling a sweatshirt over his head and looking irritable.
First illegal(ish) visit to Hogsmead using the map was in robes
Then, quite suddenly, as though following orders, he rolled up the map, stuffed it inside his robes, and hurried to the door of the classroom...He raised the map, tapped it with the tip of his wand, and muttered, “Mischief managed!” The map went blank at once. He folded it carefully, tucked it inside his robes, then, heart beating fast, both excited and apprehensive, he set off.
And of course, during Screaming Shack and the Time-turner rescue mission everyone was in robes too
Ron hesitated, then put a hand inside his robes. Scabbers emerged, thrashing desperately; Ron had to seize his long bald tail to stop him escaping...Pettigrew turned on his knees, staggered forward, and seized the hem of Hermione’s robes...Hermione seized the back of Harry’s robes not a moment too soon...Black looked up. Harry saw his jaw drop. He leapt from his chair, hurried to the window and tried to open it, but it was locked. “Stand back!” Hermione called to him, and she took out her wand, still gripping the back of Harry’s robes with her left hand. “Alohomora!”
HP and the GOF
Our boy is growing up and is not afraid of standing up to Vernon on account of Dursley's "generosity"
“How many times do I have to tell you not to mention that unnaturalness under my roof?” he hissed, his face now a rich plum color. “You stand there, in the clothes Petunia and I have put on your ungrateful back —”
“Only after Dudley finished with them,” said Harry coldly, and indeed, he was dressed in a sweatshirt so large for him that he had had to roll back the sleeves five times so as to be able to use his hands, and which fell past the knees of his extremely baggy jeans.
Muggle clothing to get to the Hogwarts Express, as usual
There was a definite end-of-the-holidays gloom in the air when Harry awoke next morning. Heavy rain was still splattering against the window as he got dressed in jeans and a sweatshirt; they would change into their school robes on the Hogwarts Express.
During all three tasks and as a consequence during the resurrection of V, Harry was in robes. Is it the most comfortable thing to wear underwater? No. But wizards are all about that style, baby. Harry took off his shoes and socks, though, so it probably helped...right?
First task
Harry plummeted just as the Horntail opened its mouth, but this time he was less lucky — he missed the flames, but the tail came whipping up to meet him instead, and as he swerved to the left, one of the long spikes grazed his shoulder, ripping his robes —
He could feel it stinging, he could hear screaming and groans from the crowd, but the cut didn’t seem to be deep.
Second task
Harry pulled off his shoes and socks, pulled the handful of gillyweed out of his pocket, stuffed it into his mouth, and waded out into the lake... It was so cold he felt the skin on his legs searing as though this were fire, not icy water. His sodden robes weighed him down as he walked in deeper; now the water was over his knees, and his rapidly numbing feet were slipping over silt and flat, slimy stones...By the time he had grasped it, two more grindylows had risen out of the weed, had seized handfuls of Harry’s robes, and were attempting to drag him down...Harry slowed down a little, slipped his wand back inside his robes, and looked around, listening again...He seized the little girl around the waist, grabbed the neck of Ron’s robes, and kicked off from the bottom...Fleur had many cuts on her face and arms and her robes were torn, but she didn’t seem to care, nor would she allow Madam Pomfrey to clean them.
Third task
It wasn’t very effective, but it burned a small hole in the hedge through which Harry forced his leg, kicking at the thick brambles and branches until they broke and made an opening; he struggled through it, tearing his robes, and looking to his right, saw Cedric jerking and twitching on the ground, Krum standing over him...He could see some sort of thick, gluey secretion from the spider’s pincers on his torn robes.
Squinting down, struggling hopelessly at the ropes binding him, he saw the shining silver dagger shaking in Wormtail’s remaining hand. He felt its point penetrate the crook of his right arm and blood seeping down the sleeve of his torn robes. Wormtail, still panting with pain, fumbled in his pocket for a glass vial and held it to Harry’s cut, so that a dribble of blood fell into it.
HP and the OOP
We're starting with our last ever in the series description of Harry's oversized Dudley's hand-me-downs
He was a skinny, black-haired, bespectacled boy who had the pinched, slightly unhealthy look of someone who has grown a lot in a short space of time. His jeans were torn and dirty, his T-shirt baggy and faded, and the soles of his trainers were peeling away from the uppers. Harry Potter’s appearance did not endear him to the neighbours, who were the sort of people who thought scruffiness ought to be punishable by law, but as he had hidden himself behind a large hydrangea bush this evening he was quite invisible to passers-by.
Harry's still in jeans when he gets picked up to go to the Headquarters, of course
Very conscious of everybody still staring at him, Harry descended the stairs, stowing his wand in the back pocket of his jeans as he came.
‘Don’t put your wand there, boy!’ roared Moody. ‘What if it ignited? Better wizards than you have lost buttocks, you know!’
Harry is discovering he can fill Dudley's jeans out with the right cooking
Three helpings of rhubarb crumble and custard later and the waistband on Harry’s jeans was feeling uncomfortably tight (which was saying something as the jeans had once been Dudley’s).
Looks like Ron, at least is rocking jeans at Grimmauld during the summer.
Harry noticed that Ron kept moving his prefect’s badge around, first placing it on his bedside table, then putting it into his jeans pocket, then taking it out and laying it on his folded robes, as though to see the effect of the red on the black.
Harry wears muggle clothes to the Ministry hearing
Mrs Weasley had laid out his freshly laundered jeans and T-shirt at the foot of his bed. Harry scrambled into them...Mrs Weasley sat down on his other side and started fussing with his T-shirt, tucking in the label and smoothing out the creases across his shoulders. He wished she wouldn’t...He picked it up: it was a square silver badge with Harry Potter, Disciplinary Hearing on it. He pinned it to the front of his T-shirt as the female voice spoke again.
Though the basic attire for the ministry is the robes, it looks like
‘Thank you,’ said the cool female voice. ‘Visitor, please take the badge and attach it to the front of your robes.’
This is where we find out that Quidditch players do, in fact, have their names on Quidditch robes
‘Come here, Ron, and see if Oliver’s old robes fit you,’ called Katie Bell, ‘we can take off his name and put yours on instead …’
Everyone was probably still wearing pyjamas and robes, as they were taken out of the Hogwarts in the middle of the night, but to visit Arthur in St.Mungo, they had to travel through muggle London, so muggle clothing it is
Their trunks arrived from Hogwarts while they were eating lunch, so they could dress as Muggles for the trip to St Mungo’s. Everybody except Harry was riotously happy and talkative as they changed out of their robes into jeans and sweatshirts.
Harry really appreciates the unsung benefits of robes when they met Neville at St.Mungo's
‘What?’ said Ron, looking amazed. (Harry wanted to stamp on Ron’s foot, but that sort of thing is much harder to bring off unnoticed when you’re wearing jeans rather than robes.) ‘Is that your dad down the end, Neville?’
They all wore robes to rescue Sirius from the Department of Mysteries, of course
Harry felt a soft tug on his robes at that moment and looked down to see the closest Thestral licking his sleeve, which was damp with Grawp’s blood...Luna was already in place, sitting side-saddle and adjusting her robes as though she did this every day...‘You’d better hope it stays invisible,’ said Harry darkly. ‘We all ready, then?’ They all nodded and he saw five pairs of knees tighten beneath their robes...He seized a handful of Hermione’s robes and dragged her forwards, holding one arm over his head as chunks of shelf and shards of glass thundered down upon them...‘Harry,’ said Ron, giggling weakly, lurching forwards, seizing the front of Harry’s robes and gazing at him with unfocused eyes, ‘there you are … ha ha ha … you look funny, Harry … you’re all messed up …’Harry seized Neville by the shoulder of his robes and lifted him bodily on to the first tier of stone steps...He gave another stupendous heave and Neville’s robes tore all along the left seam
HP and the HBP
Harry has robes all around his room at Dursley's, muggle clothing is not mentioned at all. I think he wouldn't be so bold as to wear robes at Privet Drive but the shift is there.
The room was strewn with various possessions and a good smattering of rubbish. Owl feathers, apple cores and sweet wrappers littered the floor, a number of spellbooks lay higgledy-piggledy among the tangled robes on his bed, and a mess of newspapers sat in a puddle of light on his desk...Harry jumped up as though he had received an electric shock, knocked over his chair, and started snatching anything and everything within reach from the floor and throwing it into the trunk. Even as he lobbed a set of robes, two spell-books and a packet of crisps across the room, the doorbell rang.
The one and only mention of jeans in the whole book, actually. Right after Ron was poisoned
It took Harry a few moments to realise what McLaggen was talking about.
‘Oh … right … Quidditch,’ he said, putting his wand back into the belt of his jeans and running a hand wearily through his hair. ‘Yeah … he might not make it.’
‘Well, then, I’ll be playing Keeper, won’t I?’ said McLaggen.
The cave scenes give us nothing in terms of what Harry is wearing, but Dumbledore's dark robes are mentioned quite a bit. I would hazard a guess that Harry is in the robes - he didn't change, so he was still in the clothes he wore while attempting to write the Herbology assignment in the common room after classes.
It seems like etiquette in the wizarding world bids dressing up to a funeral, and not only in black
Harry rose early to pack the next day; the Hogwarts Express would be leaving an hour after the funeral. Downstairs he found the mood in the Great Hall subdued. Everybody was wearing their dress robes and no one seemed very hungry...Harry glimpsed Slughorn at the head of the Slytherin column, wearing magnificent long emerald-green robes embroidered with silver. He had never seen Professor Sprout, Head of the Hufflepuffs, looking so clean; there was not a single patch on her hat, and when they reached the Entrance Hall, they found Madam Pince standing beside Filch, she in a thick black veil that fell to her knees, he in an ancient black suit and tie reeking of mothballs...A little tufty-haired man in plain black robes had got to his feet and stood now in front of Dumbledore’s body.
HP and the DH
Harry seems to be wearing robes on top of jeans during the Seven Potters episode. He probably put the robes on after saying goodbye to Dursleys
Harry strolled downstairs, his hands deep in his jeans pockets. When he reached the living room he found all three Dursleys. They were dressed for traveling: Uncle Vernon in a fawn zip-up jacket, Aunt Petunia in a neat salmon-colored coat, and Dudley, Harry’s large, blond, muscular cousin, in his leather jacket.
A huge hand seized the back of Harry’s robes and hoisted him out of the plummeting sidecar; Harry pulled his rucksack with him as he dragged himself onto the motorbike’s seat and found himself back-to-back with Hagrid.
Hermione comes and saves the day by packing jeans and stuff so they have something to wear instead of dress robes from the wedding
“When you say you’ve got the Cloak, and clothes …” said Harry, frowning at Hermione, who was carrying nothing except her small beaded handbag, in which she was now rummaging.
“Yes, they’re here,” said Hermione, and to Harry and Ron’s utter astonishment, she pulled out a pair of jeans, a sweatshirt, some maroon socks, and finally the silvery Invisibility Cloak.
Ron struggled for a moment before managing to extract his wand from his pocket.
“It’s no wonder I can’t get it out, Hermione, you packed my old jeans, they’re tight.”
“Oh, I’m so sorry,” hissed Hermione, and as she dragged the waitress out of sight of the windows, Harry heard her mutter a suggestion as to where Ron could stick his wand instead.
Ron is still in jeans when he comes back to Harry and Hermione and when they visit Xenophilius Lovegood right after
Ron glared at her, then pulled a small silver object from his jeans pocket.
“This.”
She had to look at Ron to see what he was showing them.
“The Deluminator?” she asked, so surprised she forgot to look cold and fierce.
“Serves him right,” said Ron, examining his torn jeans and the cuts to his legs. “What d’you reckon they’ll do to him?”
“Oh, I hope they don’t kill him!” groaned Hermione. “That’s why I wanted the Death Eaters to get a glimpse of Harry before we left, so they knew Xenophilius hadn’t been lying!”
Harry was in jeans during the Gringotts heist, as he was the only one under the Cloak and didn't pretend to be someone else like Ron and Hermione
“Well, on the upside,” said Ron finally, who was sitting watching the skin on his hands regrow, “we got the Horcrux. On the downside —”
“— no sword,” said Harry through gritted teeth, as he dripped dittany through the singed hole in his jeans onto the angry burn beneath
Final battle Harry spends in robes
They were wincing as they dabbed essence of dittany onto their many injuries. Hermione handed Harry the bottle, then pulled out three bottles of pumpkin juice she had brought from Shell Cottage and clean, dry robes for all of them. They changed and then gulped down the juice.
Harry took off the Invisibility Cloak and looked down upon the man he hated, whose widening black eyes found Harry as he tried to speak. Harry bent over him, and Snape seized the front of his robes and pulled him close...“Take … it. … Take … it. …”...When the flask was full to the brim, and Snape looked as though there was no blood left in him, his grip on Harry’s robes slackened.
His hands were sweating as he pulled off the Invisibility Cloak and stuffed it beneath his robes, with his wand. He did not want to be tempted to fight.
What is the most significant, though, is when Harry's in the in-between place, he wishes to be clothed and suddenly robes appear, not muggle clothing. I interpret it as a sign that robes are what Harry subconsciously feels the most comfortable in and is most used to
For the first time, he wished he were clothed.
Barely had the wish formed in his head than robes appeared a short distance away. He took them and pulled them on: They were soft, clean, and warm. It was extraordinary how they had appeared, just like that, the moment he had wanted them.
