Extreme Heat Guide
Getting off on the right foot
Dealing with extreme heat is similar to dealing with extreme cold, except with coolers as opposed to heaters. As your colony crashlands (this guide assumes the standard Crashlanded scenario), you'll quickly want to equip everybody and get straight to work with structures. As tropical rainforests can handily push 60C and some Arid Shrublands can even get into the mid-high 60's during heatwaves, you'll want to get a bedroom setup to tackle this ASAP.
First of all; you're either going to want to initially put everybody into a barrack, or connect everybody's bedrooms together using vents. Gather plenty of steel and components around the map, as you're going to need them for solar generators, wind turbines, batteries and coolers. You'll also want to consider setting up growing zones for food - rice and corn will do nicely for a relative stream of low amounts of food, and occasional bursts of high amounts of food. You'll also want to build a(n ideally 7x7) room for research or at least place a research bench to get passive coolers going.
Planning for success
At this point, you should have a very basic setup and you'll soon need to start producing meals. As with any other climate, you'll want to make a Butcher Table and Stove of some sort, and bill as appropriate so they'll actually be utilised. You will definitely want to consider an electricity farm also a freezer to start freezing ingredients to stop them from spoiling. As the Extreme Cold guide mentions, you'll want to build something along the lines of a 7x7 room with a centred door to start with, but leave room for expansion as your colony grows. Because you'll be dealing with Heat Waves typically within the next 7 or so in-game days after landing, you'll want to build 4 coolers and set them at -5C to compensate for warm air going in when colonists move in and out.
As for the electricity farm, you'll probably want to build 2 solar panels and 3 batteries to start, as coolers consume more power than heaters when under load (200W vs 175W). It may not be the worst of ideas to consider a Nutrient Paste Dispenser too (but only for emergencies), as all local animals will migrate during heatwaves and crops will slow down or even cease to grow if it gets hot enough. Although Nutrient Paste Meals give a -3 moodlet for '[Eating an] Awful Meal,' they give 0.9 nutrition (the same as a fine meal), and also only require 5 ingredients to make. You should also have researched Passive Coolers at this point so when the heat waves do come, you can simply stick a few in the barracks that your colonists share, or put one in connected bedrooms for every 2 rooms (assuming 4x4 bedrooms), and connect them with vents for each column or row.
Other tips moving forward
(This section for anything else of note)