Death Valley is also a bit of an outlier in it's dryness. Of course, that's what also makes it a desert. It wouldn't take much humidity to turn those temperatu

Death Valley is also a bit of an outlier in it's dryness. Of course, that's what also makes it a desert. It wouldn't take much humidity to turn those temperatures into wet-bulb of 100+ - fatal to humans. Expanding the area of this level of heat a couple of hundred miles in any direction would probably be enough.