Professor Cumulus Isobar came to Tumbleweed amidst a terrible drought caused by the spirit of Big Thunder. He promised to bring back the rains for a price. Before he could make off with the townsfolk's money, a flash flood hit the town, trapping him there.
Isobar can be seen halfway through the attraction in Tumbleweed. He is emptying water from his caravan. His caravan reads "Professor Cumulus Isobar - Rainmaker".
He is referenced in a letter found in the queue from Eberhardt Z. Marks. Marks was angry at Isobar because of a bunion cure that was sold to him - it didn't work and he hoped that he could sell him a proper remedy.
When Abigail Bullion first went into Rainbow Ridge, Isobar was standing on his caravan, promising to bring rainfall to the town. He fired his ‘rain-bringer’ cannon into the sky and sold vials of swamp root, saying that it would help. He was last seen leaving the town, taking credit for the heavy rain. Abigail didn’t buy it.
- Isobar is believed to be a caricature of character designer and Imagineer Marc Davis, though this has never been confirmed.
- In Disney Kingdoms: Big Thunder Mountain Railroad, his design was altered, with a beard, mustache, and a blue suit. He resembles Dr. Terminus from the 1977 Disney film Pete's Dragon, who was also a con artist. However, this could be a coincidence.