I spent 20+ years fishing them on the Letort every Memorial Day weekend but home was the Poconos and now is the Lehigh Valley so that is where I am most often during Sulphurs.
The Lehigh Valley streams all have them BUT on most, they won't start in earnest until the 2nd week of May. If you go the first week, NOTHING and they are done abruptly by the end of the month with surface feeding activity ending sooner and sooner in the evening as the hatch progresses. Interestingly enough, in the old days when I would drive to the Letort in late June or July, I could still catch fish on Sulphurs late in the evening where if I was back home, I am off the water well before dark by that time of year.
Like most places, the fish are a push over the first few nights but they get fussier and fussier as the hatch progresses. I caught some absolute bruisers the first night I was out this year but the next few outings it was a few nice fish and the usual dinks.
The problem for the last umpteen years has been that it always seems to rain like crazy in the week(s) leading up to the 2nd week of May and our Limestoners don't recede very quickly. While that doesn’t always preclude fishing, my notes from many years of fishing when the water was high & off tell me it isn’t always worth the effort. In addition, for me living in an area where we have 3 “major” hatches, (Olives, Sulphurs & Tricos) it is one of the few opportunities I get to do the “match the hatch” thing so I want to fish on top.
I will fish an emerger or nymph pattern in the late afternoon until I see the telltale signs of fish taking duns. I’ve used soft hackles too but to be honest, it’s hard for me to swing when there are ten fish rising in front of me. Once I am fishing on top it is either a thorax pattern or a parachute in size 16 or 18 or some other dry fly variants like Comparaduns or Iwamasa duns for the fussy fish. I usually encounter bugs with creamy yellow bodies/light dun wings or slightly olive/yellow bodies so that’s the colors I tie, but I do an all-white version of both to use when it is really dark so I can see it. I have spinners too, but never really do well with them.
It’s funny, as much as I love the Sulphur hatch and hatches in general, I’ve spent SO many years fishing in places that don’t have a lot of hatches that I actually prefer fishing when there isn’t a hatch. I'd almost rather stalk sporadic risers with a beetle or some other terrestrials than anything.
Fortunately or unfortunately depending on your preference, that time for me is about here until the Tricos start.
BTW - I'm sure you know this already but here in my neck of the woods and in Southcentral, DON'T be without a size 16 or 18 all black EWC. The "Little Black Caddis" are fluttering an inch above all of the streams in both areas and if you don't look hard and see what is happening, you will waste a lot of time fishing a Sulphur.