I honestly don't see the point of it. I don't enjoy weather names in general:
Summer, etc;
Storm; even
Gale! And rain, while very necessary, can also be destructive and, metaphorically, sad, depressing, similar to tears (isn't there a song called Blue Eyes Crying In The
Rain, where blue and rain emphasise the unhappiness?). And the fact that it sounds like
Reign, which some people also use as a name, doesn't help.
However, Botswana is permanently drought-stricken. Its flag is the cool blue-grey of water, and its currency is the Pula, which is seTswana for
Rain. Mapula (muh POO luh, with the OO as in foot, not boot) is commonly used as a given name, usually though not always feminine. So, these things can happen.