Extra-hot day requires extra water. Which you're basically gonna have to pay for. You'll bleed money. And you're gonna have to carry that water with you. Extra weight. Pressing into your shoulder. The heavier pack against your back is gonna contribute to more overheating. Your shirt soaked with sweat along the spine. (How are you gonna keep your clothes clean?)
Do you have medications which will be destroyed if exposed to excessive heat, like insulin? How are you gonna carry them and keep them cool? Do you have to carry your entire day's worth of belongings with you at all times, or do you have a friend's house or something where you can stash them? How much extra time are you gonna have to waste traveling back and forth? An extra hour this way, an extra hour that way. Gotta factor in the time. What if it's chilly overnight? Do you have to carry your jacket with you? What's for lunch? Can you bring food, or will the heat ruin it?
All sticky and sweaty from the sun, just wanna peel your clothes off and cool down in the shower? Designated times when showers are available at many shelters are periods of maybe sixty minutes, maybe twice a day if you're lucky, 5:30-6:30 AM and 9:00-10:00 PM or whatever. No other accessible times. Can't make it because you're at work? Too bad. Get off work later than that, and just wanna quickly bathe? Too bad.
Do you work full-time, clock out exhausted, and wanna take a nap in the afternoon? Find a park with shade, I guess, because you're only allowed inside the shelter between 10:00 PM and 5:30 AM. Did you get off work a little late? Too bad, you missed the strict curfew of 10:00 PM and now you're not allowed in the shelter. Can't hang out on the bus, can't linger too long at the coffee shop, can't doze off at the library. Many cities went out of their way to explicitly criminalize falling asleep--or merely sitting in one place for too long--in a park, too. Are you sick? Can't take a nap. Are you disabled? Can't take a nap. You're forced to be awake, all day. You're forced to be upright, or moving. No loitering. No sleeping. No taking your shoes off. All day. Every day.
Do you need even a quick momentary escape from the heat? Well, you'd better have money. Even if you do, you'll have to doctor your appearance, go stealth-mode, don't attract the attention of petty middle managers. The coffee shop now locks their bathroom. It's for paying customers. Maybe you bought some tea. Well, don't overstay your welcome (the boss saw your backpack and perceived that you're homeless, which means you're essentially an intruder now, so you better get out and move on soon). The university campus added card-swipe readers to all the doors, so now you can't visit the library or cafeterias. Oh shit, you spent money on the tea, so now you can't afford lunch.
You don't have a pantry, you don't have a refrigerator. No pasta, no rice, no meal-prep, no stovetop, no oven, no leftovers. So you pretty much have to eat out all the time. You'll bleed more money.
And during a heatwave, during summer in general in some climates, each day brings the same challenges and anxieties again.
Where are you sleeping? Outside? What are the cops gonna do to you? What about the sneering homeowners, skeptical of your presence in their neighborhood? Staying at a shelter? Every morning, you enter a lottery, hoping your name will be randomly selected, giving you one of the available spaces to sleep indoors at the shelter. Maybe 300 people competing for 75 available spaces. And these aren't even necessarily 75 beds, might simply mean 75 available spaces to sleep on the concrete floor. So all day long, you commute, you hide from the sunlight, you go to work. And you wonder. You worry. You don't know if you'll even get to sleep on the floor later tonight, if they don't draw your name. Should you make alternative back-up plans, identify an outdoor space to sleep in? You line up single-file at the shelter door. Required. Can't be late. Is it still hot outside? Do you need to pee? Better hold steady. (In seasons other than summer: Is it raining? Is it snowing? Is there frigid wind? You've gotta stand in line for thirty minutes.) You find your designated inch-thick cheap plastic mat on the floor. No phone charger, no power outlet. Better not lose track of your phone, your bag, your cards/cash. Leave it unattended for a minute, and not only might it get snatched, but the shelter staff themselves will toss unattended items in the trash. Stepped to the bathroom for a couple minutes? You left your water bottle next to your floor-mat, now it's gone. In the same room with you, maybe 50 people, maybe more. Some crying, some conversing, some feuding, some coughing. All night. Next morning, 5:30, the lights are on, you've got ten minutes to get up and get back outside. Oh shit, did you take off your glasses? Anything you accidentally leave behind, you'll never see it again.
And so after all of that anxiety, did you get good rest? Hope so, because it's time to get back out in the heat and do it again, and repeat the same uncertainty, precarity, dread. Will they draw your name today? Where can you get water? Get moving, you've gotta clock in at your job. Do you work in retail, in customer service? Don't forget to smile. Oh shit, is it a Sunday? Is it a bank holiday? The city's buses might not be running. So you're walking. With your pack, and your extra water, and your aching shoulder. It's ninety degrees Fahrenheit and you're in direct sunlight.