Learn English – Blow someone up

Blow here is a slang usage (originally, U.S.) meaning a break (from work, particularly, physical work).

Compare to take a breather = a pause, as for breath, and blow = cocaine or other "recreational" drugs, and stop for a puff = have a cigarette break.

I confess that after several minutes checking online, I can't be sure which of the above represents the origin of the usage, but it puts me in mind of a whale surfacing for breath (through its blowhole), so I'd go with the blow = breather route. Nevertheless, I'm sure many people say "I'm going for a blow", when they're thinking in terms of having a "smoke break", rather than a chance to catch their breath.

Personally, I find OP's cited usage slightly "odd", because to me a "blow" is a relatively short break. But I'm a BrE speaker - perhaps either AmE speakers are okay with using it for longer periods of being "off duty", or in the specific context, the speaker thinks of 12 hours as a relatively short period of free time (perhaps he's a soldier, offshore oil-rigger, etc., who's normally "at work" for weeks at a time, punctuated by periods of several days' leave of absence).

The word ‘due’ in this context would means a person or thing was traveling in the direction indicated. So a person traveling to the north from the south is heading due north, and a wind blowing due north is blowing from south to north.

Normally, winds are named for the direction they come from. So a north wind is blowing from north to south, and is expected to be cold. An east wind blows from east to west, and a south wind from the south.

While the language usage is saying the wind is blowing south to north, the more common English language convention is that a wind is described with the direction it is coming from. If you have access to the question writer, I’d ask them which they meant, because it is easy for a native speaker to mix this up. Otherwise, assume that ‘due north’ means the wind is coming from the south.