I do not fish much over the winter because I am hunting every day and that leaves limited time to fish. If I do get out it because I have seen a fish somewhere and decided that I need to have a crack at it, probably with the emergency fishing gear kept behind the back seat of my Isuzu D-Max.
When I am fishing over the winter my favourite fly is an earth worm. It is not the typical San Juan worm because it is a far quicker tie tying it the way I have tied it here.
The reason I like the earthworm so much is that it is a visible fly that attracts an aggressive response from fish, especially in high or slightly dirty water. It can scare the hell out of fish, which is not a bad thing because there is an immediate feedback loop. You either get a take or the fish spooks quickly, so you do not waste time fishing to a fish that will not take.
The Earthworm is a fly that is the first one I go to when fishing in the winter. It is especially good when the water is slightly discoloured, is coming up or it is raining. Fish hammer hell out of it when the conditions are right.