I am out on Long Island and my dahlias have been producing since June. That is a record for me.

Some still have not bloomed here in Baltimore County.

Some still have not bloomed here in Baltimore County.

msbumble do you start them early then put establised plats outside?

I have never started them early - I plant them directly in the ground after last frost date. In past years certain varieties have put out more flowers than I can keep up with - none did that this year.
Isn't Long Island always a little cooler in summer because of ocean breezes? I've always assumed it's a gardener's dream location. And because dahlias seem to be happy in the NW (who isn't?), maybe LI is the next best thing.
The humidity tends to hang in the air here (think Louisiana) but refuses to rain. The green parts of my plants appear healthy though, just few or no flowers.
Baltimore Cty, isn't this later than normal for you? I'm sure you had some high temps this season.

Yes the gulf stream keeps our weather some what less in eather direction. It was very hot here this summer. My thought is that established plants tend to hold up better, When it was very hot the flowers went to open centers very fast. The minute the weather cooled they went crazy. I have another reason to plant established plants out. We have a very bad slug problem. Over night they will strip a new tuber bare and it will never produce stems again. When the plant is big enough I can spray amonia and water at 11oclock at night and still haver a plant in the morning.

yes hot and humid day after day.

Not as nice as other years. We had horrific hot days with lots of humidity.

So-so for me. Established plants seemed to slow way down; the others went into suspended animation till the nights turned cooler and then they bloomed their little hearts out. I'm still learning, and don't think I fertilized enough. I was also afraid of overwatering, so I probably could have given them an extra drink on those really hot days. I grow mine mostly in pots. Tuber production was excellent and digging was a breeze.