Why do people duck when it is raining?

Question

It is raining is NYC and I noticed that many of the people who didn't have umbrellas were trying to duck from the rain drops. I for one have never done that, but I am curious as to why people do that.

Answer 1

It is better to have a wet back than a wet front.  It may be just instinct to show your back to danger or in this case rain to protect the more vulnerable parts.  

Answer 2

Because they're silly and they've seen other silly people do it.

Answer 3

instinct to conserve heat

Answer 4

In order to prevent the rain drops from hitting the eyes so that they can keep the eyes open and walk without any difficulty.