You could survive nearly any extreme heat/ wet bulb event without power with under $500 worth of equipment…

With a couple hundred watts of solar panels ($200), a modest sized power bank/solar “generator”($250), and a cheap table top ice machine ($60-100). This assumes of course that it will be sunny, but given we are talking about extreme heat that’s a reasonable assumption. You could also run it off a car inverter or a generator, if you have fuel. You could make ice during the day and store it in a cooler for nights. Bagged ice in armpits/groin, ice baths, etc.

Also cold drinks!

Based on a couple hundred watts of solar panels, a solar “generator” with an inverter that will output a couple hundred watts. According to specs they use around 150-200 watts. And I’m talking about a small thermoelectric ice machine not a compressor driven one or one that also keeps the ice cold.