"Of COURSE it's hot up here!"
That came out louder than Babs had intended. And definitely sharper than she'd intended. She'd downright snapped it at you. But she couldn't really feel sorry for it.
Gotham was in the middle of an unprecedented heat wave, and nobody was enjoying it. It had been over a week of miserable, muggy, sticky heat. It was, as Dick kept saying, 'the worst'. On the one hand, not as many people as usual were out doing criminal activities, so that was nice. On the other hand, they were reaching the point where the heat was starting to cause infrastructure problems, so it wasn't like Gotham was catching a break.
Bruce was - and rightly so - insisting that patrols kept up, and the GCPD always had alerts to attend to, and Oracle's system never slept. So, just like she would be any other night, Babs was up in the clock tower, sat in front of her monitors, working.
The problem with one's hideout being at the top of a tall tower: heat rises. The problem with one's hideout being packed to the brim with top-of-the-line electronics and generators and backup power sources and anything else you could practically think of: all of that stuff generates heat.
The Watchtower is an oven, is the point. There's only so much you can do with portable fans. She's on, like, her sixth bottle of water tonight, already cut down to 'it's only turned on if it's absolutely necessary', and she'd been wondering not for the first time if this heat wave was going to be more than even Wayne Enterprises' cooling systems could pull her computers through.
So your probably-casual statement of, "Wow, it's hot up here," when you'd stopped by had kinda made her snap, a little bit. It's out of the norm for her, but the heat is making her grumpy.
"It's hot everywhere! I don't think there's a single spot in the city that is not hot right now. But thank you for the observation," she grumbles, sarcastically. "Can I help you with anything, or are we just going to discuss the weather again?"
