Is it too late to see fireflies near Tokyo?

Firefly season snuck up on me this year and I'd like to go see them but most websites say the firefly season ends early July, is it still worth it?

I was thinking of visiting Torodoki Valley since I could go in the evening after work but it seems like part of it is closed? I also thought about visiting Chiba over the weekend but I'm afraid that's leaving it even later 🙁