This is a simplified guide to some of the major hatches that occur on our water, approximate sizes are included to help when selecting a fly or building a specific Usk fly box.
The list is not exhaustive, and it is important to note that chironomids are present throughout the season – being particularly important in the warmer months. Various small and medium olives will be seen from May onwards, these can typically be covered by an olive upright or general olive pattern in size 16-18, then if you are unlucky enough to encounter the angler’s curse – caënis – you may get away with fishing a small size 18 olive pattern as the light fades.
Depending on the weather and seasons, months can run into each other – so it is worth carrying your April flies with you in early-May and so on until the close.
| Month | Typical hatches |
| March | Grannom (s14), March brown (s14), large dark olive (s14) |
| April | Grannom (s14), March brown (s14), large dark olive (s14) |
| May | Large dark olive (s14), olive upright (s16), caddis/sedge (s16), mayfly (s12), large brook dun (s14), yellow may (s14) |
| June | Olive upright (s16), caddis/sedge (s16), mayfly (s12), large brook dun (s14), blue-winged olive (s16), pale watery dun (s18), yellow may (s14) |
| July | Caddis/sedge (s16), large brook dun (s14), blue-winged olive (s16), pale watery dun (s18), yellow may (s14) |
| August | Large dark olive (s14), large brook dun (s14), blue-winged olive (s16), pale watery dun (s18), yellow may (s14) |
| September | Large dark olive (s14), pale watery dun (s18), yellow may (s14) |