My problem with this sentence is that in English it is hard to distinguish the idea that there has been a whole day without any rain from the idea that it has been raining during the day, but not constantly.
I think the Spanish must mean "it has not rained at all today".
Is it the case that "ha llovido" implies that we are talking about today rather than a day some time in the past?
depending on the country, and the speaker, 'y' and 'll' may be pronounced 'y', 'j', or 'zh.' In Argentina all y's and ll's are always 'zh.' In the US I watch Spanish programming on Univision and Call now! = llama ya = yama ya or jama ja or zhama zha, depending on the speaker In the same town in Mexico some people say 'yo' as yo, some say 'zho'
But we are not doing word by word translation here. "It hasn't rained the whole day." and "It has not rained all day." have absolutely interchangeable meanings in English. Even "It has not rained at all today." is still talking about the same fact that there was no rain the entire day.