Heat was paramount.
Sure, heat wasn't infinite. Heat couldn't make it into apartments at night, for instance, which meant that people who took refuge there were safe, at least until daybreak. It couldn't be everywhere, but it could be enough places so that, even if someone hid in an apartment at night, heat would get them eventually. The smart ones knew it: heat wasn't up for discussion. Find ways around it, evade it for a while, seek shelter, drink water, cool down; it doesn't matter. Heat would win out in the end.
Felix and Josephine didn't know that. It was early morning, two or three, and they were hiding in the cover of an alley. The concrete was cool, even if the air was stifling, so they sat and watched the stray cats playing around the dumpster.
Josephine got up, walking over to the dumpster. She hopped on top lightly while the cats scattered. She jumped and grabbed the rusty iron fire escape that clung so precariously to the alley wall. Swinging her feet up, she pulled herself, rung by rung, until she sat on the bottom level of the metal contraption.
Felix watched her, half-amused. "What's going on up there?" he inquired, doing his best impression of what he imagined to be a grin.
She replied, "not much. You want to come up?"
He looked around. "I'm good down here."
"Yeah," she said, drumming a little cadence on the fire escape, "I figured."
"What does that mean?" he asked.
"What do you think it means?" she exclaimed, exasperated, "you just don't seem like the type to do something really adventurous."
"I hang out with you," he said.