Keeping Cool! is a magazine story.
One baking hot day, Thomas chuffed along his branchline with Annie and Clarabel. Soon, Thomas began to go slower and slower and on closer inspection, the driver finds a leak in the water tank. Before long, Thomas was running low on water and the guard tells the passengers what's happening. One of the passengers is a toy salesman who gives the guard some clay to plug the leak. They carried on to a nearby duck pond and, using a fire bucket, the driver, fireman, and guard get water to fill the tanks. Later, Thomas visits the maintenance shed and is mended properly.
The warm weather stayed for quite some time and the duck pond began to dry up. Thomas tells the Fat Controller about the poor ducks. Sir Topham Hatt knows how to help and soon Thomas is coupled up to a tanker. The Fat Controller then jumps aboard Thomas and they set off for the duck pond. Once there, the water from the tanker was emptied into the pond and it was soon full again!