As a Brooks saddle owner I have never worried about using it in the rain. Applying 'proofed' from time to time seems to provide a fair degree of water resistance. I have cycled for hours throughout the night in almost constant heavy rain and my faithful Brooks saddles have always survived socially to live another day. However, a recent trip to 'Decathlon' saw me purchase a waterproof saddle cover.
I cannot imagine what drew me to this cover?! It is quite bight and having splashed some water over it, it is definitely waterproof as the water just beads off.
The fit is quite tight but it isn't hard to get on or off and weighing next to nothing it can easily be left in my saddle bag for times when the heavens open.
The good thing about this cover it that it stays in position when placed on the saddle and is comfortable to ride on.
At £3.99 it is fairly inexpensive and for me is a bit of a bargain.