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.