Is it a learnt trait?

I have noticed over the last few days of poor weather (rain) that all my adult hens run for cover back to the coop and indoor roost, but the chicks dont bother.  They are quite happy to get drenched and roam the garden in the pouring down rain, although they do dive for cover when it is torrential under densely leaved bushes.

Is running for cover back to the coop something they learn in time or are these girls water lovers?

They have been living in the coop for a while now with the other hens and they know where to go on a night without too much trouble, but for them going in there when it is raining it is proving problematic. 

Are they OK to be left to get this wet or should I be encouraging them to go inside?

Thanks.... there are 4 ex batts and 2 laced wyandotte bantams who share the coop.
It has a 10' x 10' run and is 5' high at its lowest and 8' high at its highest point.  Over 15 different roosts to choose from and plenty of ground space.

The bushes which they are taking cover under are so densely leaved that it is perfectly dry under there and they do have other places in th garden to get away from the bad weather.

(I have found the big girls in one of the rabbitries before now (getting in through a fully open window which is always open to create airflow) which is 20' x 14'

I shall see if I can guide them to somewhere which might not at somepoint cave in under the water on the leaves... LOL