How often to Sandy tours at Rock Harbor sell out?

[PictureYellowstone]

I'm trying to build my itinerary for mid-August.

And I'd like to do at least two tours in one day.

I see that tours aren't available for purchase in advance, my question is do they still often sell out?

How far out can people by them once they reach the island?

Thanks for any info!

[Ingo]

Page 10 has the Sandy schedule: https://www.nps.gov/isro/upload/Web-Rea ... nstone.pdf
I would call the lodge about when you can purchase tickets and demand. The one time I took a tour some years ago we signed up in the lodge office the day before--they just kept a list in a notebook.

[Bobcat1]

As soon as you arrive at Rock Harbor, go to the lodge office and sign up in in a notebook they keep. Actually, it may be more likely that an excursion is cancelled for lack of people than that it is sold out. The one time I did a tour (Passage Island), it was pretty full.