Re: 'Be,' and it is!
"Be and it is" for Adam (as) was not just a word by Allah and having Adam (as) appearing like magic before the anegls....
the angels collected the mud (clay, whatever) and then Allah formed it into a shape and then came the soul....
"Be and it is" did not exactly mean an instantaneous emergence of Isa (as) from this air....
"Be and it is" was followed by a normal 9 month pregnancy and delivery to bring Isa (as) into the world....
"Be and it is" is also not the case for falling of rain....
like angels had to collect the ingredients for creating Adam (as), like an angel had to go to Mariam (as) and tell her and then Mariam (as) had to bear the pains of labor, similarly Mikail (as) does the required jobs for the rain....
perhaps he wud be the one moving around the clouds and causing the correct conditions for the rain to fall, and when Allah wants rain to happen, He says it and it falls....
and sometimes, when He does not will, we say heavy loaded dark clouds pass over our heads without pouring a drop on us....