May is generally a much more pleasant month to go fishing. Unfortunately it can often disguise itself as April (or even February for that matter) for the first couple of weeks. But at some point during the month you can be pretty sure to see a rise of sorts. It might not be the ecstatic rises of summer evenings, but any rise is at least a little exciting.
The water (hopefully) has warmed up sufficiently to enable the fish to be actively searching for food. And generally they find it in the way of buzzers and hawthorn. Of course, nearer the end of the month other food starts to appear in quantity; sedge, damsels, caenis and, if you are lucky enough to be on the right water, lake olives.