CANNES, France — In Cannes, the weather changes so fast that you can enter a theater in sandals and exit in desperate need of rain boots and a scarf. On Friday, I ran to my room to grab a warmer shirt for an overcast outdoor party. I checked the window and added a jacket, then checked the window again and was stunned to see the sun. By the time I raced back down the Croisette (in something sleeveless), the cocktail hour was over. C’est la vie.

The mutability is a lovely parallel for the filmgoing itself. At the end of a great movie, you feel like the world has changed. And when a film is bad, the director suffers the shock of their forecast being dramatically upended. Before the premiere, they were chauffeured around in festival-sponsored BMWs and now their friends are stammering how much they like their shoes.

Harris Dickinson, the young British actor who convincingly dominated Nicole Kidman in last year’s “Babygirl,” seemed a tad flustered introducing the premiere of “Urchin,” his directorial debut. Jacket and tieless with his dress shirt’s sleeves rolled up lopsidedly, he hastily joked, “I’m nervous, but I hope you enjoy it — and if you don’t, tell us gently.”

That barometric pressure is especially intense in Cannes, but onscreen (so far, at least), the wind is only blowing one way: south. Almost every film so far has been about a character braving a storm — legal, moral, political, psychological — and getting dashed against the rocks.

“Eddington,” Ari Aster’s twisty and thistly modern-day western, is set in New Mexico during that first hot and crazy summer of the pandemic. To his credit and the audience’s despair, it whacks us right on our bruised memories of that topsy-turvy time when a new alarm sounded every day, from the social-distancing rules of the coronavirus and the murder of George Floyd to the rumors that Antifa was rioting in the streets. With “Hereditary,” Aster made horror trauma hip; now, he’s shifted to satirizing our shared PTSD.

Joaquin Phoenix stars as Joe, a sheriff with a soft heart and mushy judgment, who rejects the mask mandate of Eddington’s ambitious mayor (Pedro Pascal), arguing that COVID isn’t in their tiny rural town. Maybe, maybe not — but it’s clear that viral videos have given him and everyone else brain worms. Joe’s wife (Emma Stone) and mother-in-law (Deirdre O’Connell) are fixated on conspiracies involving everything from child trafficking to the Titanic. Meanwhile, Eddington’s youth activists, mostly white and performative, are doing TikTok dances advertising their passion for James Baldwin while ordering the town’s sole Black deputy (Micheal Ward) to take a knee. No one in “Eddington” speaks the truth. Yet everyone believes what they’re saying.

Phoenix’s Joe watches Henry Fonda movies and wears a symbolic white hat. Yet, he’s pathetic at maintaining order, pasting a misspelled sign on his police car that reads: Your being manipulated. Having lived through May 2020 and all that’s happened since, we wouldn’t trust Aster anyway if he’d pretended a savior could set things right. Still, there’s no empathizing with hapless, clueless Joe when he whines, “Do you really think the power is with the police?”

Well, one person in a Cannes film does: the lead of Dominik Moll’s “Dossier 137,” a single mother named Stéphanie (Léa Drucker), who just so happens to be a cop herself. Once, Stéphanie investigated narcotics. Now, she gathers evidence when her fellow officers are accused of misbehavior. An inspired-by-a-true-story detective movie set in the aftermath of the 2018 Paris demonstrations, the film’s central case involves a squad of undercover officers who allegedly shoot a 20-year-old protestor in the head with a rubber bullet, shattering the front of the boy’s skull.

Moll has made the kind of sinewy procedural that makes your palms sweat. “I have no personal feelings,” Stéphanie insists, even as her ex-husband and his new girlfriend, also police officers, accuse her of being a traitor. More precisely, she allows herself no visible emotions as she questions both the accusers and the accused. It’s impressive to watch the meticulous and dogged Stéphanie put together the pieces and make the liars squirm. But she’s the last person in the movie to see the big picture: No matter how good she is, she can’t be a hero.

Aleksandr Kuznetsov in the movie “Two Prosecutors.”

(Festival de Cannes)

Sergei Loznitsa’s Stalin-era drama “Two Prosecutors” lugs its own protagonist along that exact same journey; it’s affixed to cynicism like a train on a track. Here, the ill-fated idealist is a recent law student (Aleksandr Kuznetsov) who wants to interview a prisoner that the government would rather remain disappeared. The voices that once boldly spoke out against the Soviet regime have long since been silenced. Now, the Great Purge is locking up even the Russians who swear they love their leader.

Methodical and dreary, the film’s key image is of Kuznetsov (who coincidentally-but-on-purpose has a nose that appears to have been busted around) walking down endless dismal hallways. He’s polite and stoic, but we all know he’s not getting anywhere. The film plays like a sour joke with an obvious punchline. I respected it fine, but slow and inevitable don’t make great bedfellows. The jet-lagged stranger next to me nodded off for a nap.

Snores weren’t a problem at “Sirât,” a nail-biter that had its midnight crowd wide awake. The fourth Cannes film by the French-born Spanish director Oliver Laxe, it’s about dirtbag ravers who’ve gathered in a barren stretch of Morocco for a stunning party: orange cliffs, neon lights, thumping EDM beats and dancers thrashing in the dust like the living dead. The only sober attendees are a father (Sergi López) and his young son (Bruno Núñez) who are hoping to find the boy’s sister, a bohemian swept up in the relentless rhythm of this road-tripping bacchanalia. But when the party gets busted up by the police, this fractured family joins a caravan headed in the vague direction of another fest. Next stop, disaster.

An image from the movie “Sirât,” directed by Oliver Laxe.

(Festival de Cannes)

The small ensemble cast looks and feels like they’ve already lived through an apocalypse. Two of his actors are missing limbs and nearly all are flamboyantly tattooed. As these battered vans hurtle through the desert, it’s obvious that “Sirât” believes the age of “Mad Max” has already begun. But Laxe’s cadence of death is nasty and arbitrary and delightful. He’s unconvinced that we can form a community able to survive this harsh world. At best, he’ll give us a coin flip chance of success. I’ve got to watch the film again before I decide whether (a) it’s a comedy and (b) it has anything deeper to say. But a second viewing won’t be a hardship. Even if “Sirât” proves half-empty instead of half-full, witnessing another audience gasp at its mean shocks will be sweet schadenfreude.

Which finally brings us back to Harris Dickinson. His film “Urchin” is good. Great, even. The last time he was in Cannes, it was as the lead in Ruben Östlund’s “Triangle of Sadness,” but he’s a real-deal director. It’s high praise to his acting that I don’t want him quitting his day job just yet.

“Urchin” lopes after a drug-addled boy-man named Mike (Frank Dillane, fantastic) who’s been sleeping and scavenging on the London streets for five years. Yes, Dickinson has gone 21st-century Dickensian; Mike pesters people for ketamine, vodka and spare change like Oliver Twist begged for porridge. But this isn’t a pity piece. “Urchin” is energetic and filled with life: funny asides, tiny joys, stabs of recognition and flourishes of visual psychedelia.

Mike is given multiple chances to change his fortunes. Yet, he’s also stubbornly himself and we spend the running time toggling between being scared for him and being scared of him. Dickinson, who also wrote the film, wants us to know not just how easy it is to slide down the social ladder but what a small step forward looks like, even if his tone is ultimately more Sisyphean than self-help.

After the movie, I ducked into the drizzle, then into a cafe. A man was monologuing to an acquaintance about his career change from tech to film and this is my favorite place to eavesdrop.

“I was rich and successful but I had to look for something more jazzy,” he explained, stabbing at the other person’s plate of charcuterie. He’s now broke, he said, and divorced. But somehow, he seemed content. He’d emailed his script to Quentin Tarantino. Maybe next Cannes, he’ll be the one getting fêted and chauffeured. Maybe the wind would start blowing his way. A great movie really can change your life.