A Short Hike. Essentially a short, cute animal-characters "collectathon" walking-sim/3d-platformer with some low-stakes "arcade" bits here and there. The low-res pixel-effect can be turned off.

AER: Memories of old. Quite a bit in same vein as Rime/Sable, travel between floating islands and participate in low-stakes puzzles/platforming. Pretty charming, imo... and short. Can be finished under 2 hours.

Stardew Valley but you have to keep your inner micro-manager under check

"A Short Hike" for sure, "What Remains of Edith Finch" could fit and nobody mentioned it.

Superflight is great and quite different from most of the suggestions you are getting.

(The Stanley Parable I don't think fits but if you want to try it out I suggest you do not take the "Deluxe" version and sitck to the original one)

Dave the diver!

I'd recommend:

• The Outer Wilds
• Graveyard Keeper
• Subnautica

Psychonauts (the original, not the sequel, though the sequel is also good) is a Summer Camp themed 3D platformer. It doesn't quite meet your "low stakes/chill gameplay" criteria as it does have combat and mildly challenging boss fights and platforming, but it nails the rest. It's easier than Tunic. Maybe worth checking out.

Brothers: A Tale of Two Sons strictly meets all the criteria listed, but it's ultimately a tragic story. If "some kind of impact" includes leaving you in tears, check it out.

Okami is a Zelda style adventure set in feudal Japan with immaculate vibes. You play as the sun goddess Amaterasu in the form of a wolf bringing light and life to a land ravaged by demons. The world is cold and dark at first, but you bring spring and summer on your heels.

Finally, two favorites from my childhood are the Spyro series and the Ty the Tasmanian Tiger series. These are 3D Platformer collectathons and neither of these series are even close to any of the examples you provided, but they are bright and colorful and in my heart they have feelings of Summer Vacation and staying home all day to play video games.

"Alba: A Wildlife Adventure" jumped to mind. I don't remember it being long or difficult, but I had a nice time.

Firewatch. A summer-themed walking simulator with an interesting story.

I'd say Night in the Woods, but that may be a very late summer / fall kinda vibe.

Lil Gator Game sounds right up your alley.

My Summer Car is pretty cool. I've been playing Dredge this summer and it's been pretty chill and low-stakes.

Dungeons of Hinterburg might fit the bill. Just released. Looks and plays well. It is an action rpg with social sim elements set in the Alps.

The Uncharted series? It's okay to play on an easy difficulty level, and they're not too hard anyway.

A Short Hike
Alba: A Wildlife Adventure Wide Ocean Big Jacket FEZ Night in the Woods Before Your Eyes

My summer car

If you haven’t played outer wilds yet, do it. Go in blind, read/watch nothing unless you are absolutely stuck. It truly is one of the best video games ever made, and it’s definitely a cozy adventure (for the most part).

Edit: the reason you need to go in blind is because all progress happens in your own head. Once you know something you can’t un-know it. Replayability is pretty much zero.

Also, controller is 100% mandatory. Not keyboard and mouse, not even HOTAS. Controller, preferably with axes for the triggers (not buttons like the switch)

Far: Lone Sails and Far: Changing Tides

Hyperbolica

Spiritfarer

Jazzpunk

Dreamfall Chapters

Manifold Garden

Fract OSC

Outer Wilds

The Oregon Trail or the recent remake or Organ Trail

The gameplay might be a little more tense than you're looking for at times, but Kena: Bridge of Spirits gives me summertime vibes.

For something with chiller gameplay, maybe Yakuza Like a Dragon? (I haven't played Infinite Wealth yet, but the setting also seems promising.)

I'm not sure if this is the best recommendation looking at your criteria, but Slime Rancher (1 and 2) are chilled games that have beautiful and colourful visuals. To me it feels like a summer vacation - one where you're staying at a farm and catching adorable slimes.

Another recommendation I'd have is Tearaway unfolded. It's a super charming adventure in a papercraft work. It really stuck with me and felt like an adventure. It's only on PS4/5 as far as I'm aware though, but if you happen to have one of those I guess you could cast it to your Steam Deck using Chiaki. Or on the off-chance that you have a PS Vita, the original version of the game was on there.

The Long Drive and My Summer Car are literally everything you describe wanting in two distinct flavors.

I also was immediately thinking "The Quarry," which is essentially a playable horror movie set at a summer camp. I don't usually like these types of games, but this one is extremely good if you like horror movies.

Tchia just oozes summer vibes, and is inspired by the culture of New Caledonia. No failing, tons of extra accessibility options, skip gameplay segments if you feel like it, autoplay QTA's, and so on.

Personally I like a little bit of a challenge even in my cozy games, but Tchia has so much character that I didn't mind.

I think you might like Superliminal or Hardspace Shipbreaker.

I'm less sure about the following but still wanted to suggest them:

• Dinkum (it's like Animal Crossing but in Australia)
• Astroneer (pretty chill exploration and mining game)
• Roots of Pacha (a more story-focused Harvest Moon like game)

Psychonauts 1/2. The first game literally takes place at a summer camp. Second one has basically the same vibe.

• Slay the princess
• Until then
• Coffee talk
• Detroit Become human

The last one is more like an interactive movie than a visual novel, but it is still pretty cool

You could check Full Throttle from Lucas art. It's old but it feel like hot weather 🌡️

Likely in the ok-ish section but Celeste has that vibe going for it

Funny that you mention Life of Strange because it’s actually set in Autumn, but it does kinda have the vibes you describe. What does have way more summer vibes though is the prequel, Before the Storm, totally worth it if you’ve haven’t played it.

Try Eastshade, should check all the boxes IMO. https://store.steampowered.com/app/715560/Eastshade/

Any game from Amanita Design might fit the bill too (Machinarium, Botanicula, etc.).

If you don't mind reading a lot, there's Roadwarden https://store.steampowered.com/app/1155970/Roadwarden/

Maybe the Yo-Kai Watch games? They are RPGs probably inspired by Pokemon, but better in basically every way.

You play as a kid befriending Yo-Kai (creatures taken from japanese folklore), while exploring a pretty cool city. Has a nice soundtrack as well. The story of the first game is kinda meh, but I think it still has that summer vibe.

The second game is a lot better, with an actual story, more stuff to do and more to explore. Definitely the better game, but playing it first might make the first one less enjoyable afterwards.

Both of these games have that childhood summer adventure vibe, even though I myself didn't spent my childhood befriending Yo-Kai.