To address the CIA webpage question: What's interesting to note is that the part of the site that says the LeMay leaflets were dropped prior to Hiroshima is only a caption:

Front side of OWI notice #2106, dubbed the “LeMay bombing leaflet,” which was delivered to Hiroshima, Nagasaki, and 33 other Japanese cities on 1 August 1945.

It raises the question: Did the author of the piece (Josette H. Williams) actually assert this was true as part of her research? I was surprised to find (only because I did not expect too many people would care about that particularly detailed a question) a while back that the answer was available on another website dedicated to various psychological warfare leaflets:

There has always been a rumor that Hiroshima and Nagasaki were warned of the coming bomb raids. The rumor is wrong because as Enola Gay pilot Colonel Paul Tibbets once said in a private conversation with Hubert’s daughter Jo Williams:

Hiroshima was not warned because the secret atom bomb was to be delivered by bomber devoid of any defense weapons and the Allies could not jeopardize the success of the historic mission by advertising - especially since they rightfully felt the newest weapon would end the war and save thousands of Japanese and Allied lives.

It is easy to see where the rumor started. Jo Williams wrote an article on the bombing campaign that was published by the CIA. She told me:

I did not want to discredit the CIA but since the article has become part of the National Archives it deserves correction and clarification. The text of my article was purposefully ambiguous but under a picture of Leaflet 2106 the CIA inserted a line specifically citing Hiroshima and Nagasaki as being among the 35 cities which were warned ahead of being bombed. This is simply not true. The insertion was done after I approved the final copy for the press. Still, it carries my name so I guess I should have a right to correct it. I shall write the CIA editorial offices with the correct information and they can go as national as they wish with it.

So even the author of that piece declaims that particular assertion! It is interesting that the CIA editor decided that little falsehood ought to be inserted there. I have found nothing to suggest LeMay leaflets were ever dropped on Hiroshima. Even if they were, it is irrelevant to the warning question, since LeMay leaflets specifically name their targets on the front, and Hiroshima and Nagasaki were never included on any of them.

It is of course possible that some kind of generalized leaflets were dropped on Hiroshima and Nagasaki as part of the psychological warfare campaigns. The Hiroshima Peace Museum has a leaflet that is captioned as having been dropped — it is, if I remember correctly, Leaflet 2014:

This leaflet could have been a bomb.

This is to warn you away from military installations, factories,railways, and harbors where our bombs will strike again and again until the gumbatsu quits this hopeless war.

Stay away from military objectives!

Which would not have been very helpful at Hiroshima or Nagasaki (where the bombs were dropped in the center of civilian areas) in any case.

Hi, I'm the maker of the video - he pointed me towards this because of our discussion in the comments.

I'd just like to clarify what he's saying I say in the video.

There is a difference between the Lemay Leaflets, with the B-29 dropping firebombs - which are reported to have been dropped on Hiroshima, Nagasaki, and 33 other cities.

And the post-Hiroshima "we are in possession of the most powerful explosive" leaflets picturing the Hiroshima explosion - which were reportedly dropped on Nagasaki a day too late, but multiple other cities in order to encourage unconditional surrender.

I do not say, on purpose, that the nuclear warnings were dropped on Hiroshima or Nagasaki. But rather, the generalized warnings were.