Huge is a 5 mile object. That would end most life. If a month away at 40K mph, that would be 29 million miles, half the way to Mars. Only a dot in the largest telescopes on Earth or in space. Hard to believe most anyone besides searching scopes for it would have a chance to see it two months away at 60 million miles when it is as small as a moon of Mars.
And at that range, uncertainty if it would hit, or where. But if it might hit, could end most large animal life on planet. That includes everything above 5 lbs in weight for terrestrial animals. Might get a global fire storm and then a total winter over everything but tropical oceans. Might last a decade.
With no way to stop it within the 2 month window or even less, no point worrying anyone for that time length. Especially when any survival chance is so slim and not very pleasant. Living will envy the dead.