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At least two folks pointed out this effect, which cools the air before it crosses the hand. Great point! And by the way, this effect was crucial for landing the Viking spacecraft on Mars.../1
2/ Research showed the rocket exhaust during Viking’s landing would blow too much soil and make too large craters. Since Viking had no rover, it would be unable to get away from those craters, and that would mess up the science. (Mock-up with Carl Sagan, here) 
3/ So to reduce this effect they replaced the engine nozzles with these “showerhead” nozzles. These would create lots of smaller jets instead of one large jet per engine.
4/4 That would allow the jets to mix turbulently with the surrounding Martian atmosphere a lot more, causing the jets to taper off and come to an end at a shorter distance from the engines. That way they would not be digging craters in the soil from as high up during the landing.
