You'll need to cite sources for Chicxulub or any other impact producing temperatures like that globally. It is thought that Chicxulub may have produced global

You'll need to cite sources for Chicxulub or any other impact producing temperatures like that globally. It is thought that Chicxulub may have produced global firestorms, before a period of global cooling. The point still stands: it's not hard to build structures that can survive fire. Building out of concrete, with thick walls, a self-contained air supply, and away from any vegetation (or simply underground) should suffice, and will still be much easier than colonizing Mars.