Bucky Fuller believed it was possible to create aerial structures which supported water reservoirs (tens of millions of gallons).
Using the same principles that allow battleships to float even though they weigh thousands of tons outside the water.
They would need to be enormous several thousand feet in diameter. The whole structure would be enclosed so the internal air pressure could be elevated to several degrees above external temperature.
It would be a significant engineering challenge. Yet, the benefits of having a steerable lake to deploy above fire zones might save a lot of money in the long run. If you could put out a fire that ends up costing billions of dollars before it causes that much damage...