Headcanon: Hal wears his dad's jacket constantly — every season, every mission, rain or shine. But it gets worse after he gets the ring.
Here's the thing: one of the ring's core functions is environmental regulation. It's what keeps him from freezing or burning up in the vacuum of space, in the atmosphere of some hellscape planet, whatever the mission throws at him. But that regulation doesn't just switch off the second he's back on Earth. Ring on, temperature stops being a variable — doesn't matter if it's July in Coast City or the middle of a Gotham winter, he's just comfortable. Always. As long as he's got the ring, the jacket's basically decorative.
Naturally, the League notices. Constantly.
Barry catches him lounging in it during a heatwave and just stares. "Hal. It is ninety-five degrees. You are wearing leather." Hal doesn't even look up from what he's doing.
Diana asks once, genuinely curious rather than exasperated, how he doesn't shiver during a snowed-in stakeout in Gotham while everyone else is bundled in three layers. He just shrugs like it's nothing.
Oliver doesn't ask so much as complain — he's freezing his ass off on some rooftop in nothing but his usual sleeveless getup, pride refusing to let him admit it, and Hal just stands there next to him looking completely unbothered. "You could just tell me the trick, Jordan." "Could. Won't." Oliver mutters something uncharitable under his breath.
Bruce, predictably, just watches him for a solid five seconds too long before deciding it's not worth the effort of asking directly, which somehow annoys Hal more than if he had.
And every time Barry and Oliver end up in the same conversation about it, it devolves fast — Barry insisting there's obviously a scientific explanation, Oliver insisting Hal's just being smug on purpose, the two of them bickering while Hal watches with the deep, quiet satisfaction of a man who started absolutely nothing and takes credit for all of it.
Every time, Hal gives some version of the same answer: "Guess I'm just too cool for that." He knows exactly why they're asking. He never actually explains it. He just likes watching it drive them slowly, quietly insane.