This is a very reliable perrenial for me that reseeds and is in bloom by mid august in my climate (zone 3). Im not sure how it would handle your wet humid summers but give it a try for sure.

You're at the very borderline for Rudbeckia, and it is questionable how much nectar they'd produce in your climate. Not to mention root-knot nematodes.
If it's yellow you're after, try Thryallis or California Daisy.

John

Thanks, John. I have a thyrallis. I like its color and it is a perennial in my garden. It doesn't seem to attract butterflies or hummingbirds though. I had a California Daisy before and it got very big with little attention from butterflies.

Thanks for the heads up regarding the possible nematode problem. I will plant the Black-Eyed Susans in very rich soil and hope they make it through one season at least.

It's not easy to find yellow plants that really attract butterflies.

What about perennial sunflowers? Downy Sunflowers or Maximillian Sunflowers are perennial and extremely hardy. The Downy will also reseed and spread by rhizomes until you have a veritable forest of yellow. Bumble bees definitely love them, so I don't know why butterflies wouldn't. I don't have enough sun to keep them happy, but I used to love their cheery yellow blooms.

Martha