It could be too much nitrogen in your growing medium. Raise the potassium levels and fruit production will be shifted into a higher gear. Nitrogen grows beautiful foliage, but too much can hinder fruit development.

Ted

I had lots of tomatoes ripening daily when the temperatures hit 100F each afternoon. Now that temperatures only get to near 90F green tomatoes just hang there for two weeks. I asked on this forum and the one response was that 90F should be an ideal temperature. This time the answer seems to be potassium. Hummm?

MMMM! From what I read on the Florida Gardening site, they stop fruiting at 90 degrees. Sorry I don't know why this is happening to you. I grew 3 types of heirloom tomatoes this year and I really wasn't impressed with how they grew or how little they produced or how they tasted had a well composted hugel. The basils and flowers grew like crazy.

I think, the high temps can hinder new fruit setting, but with the existing fruits, as long as plant is fed and watered, it should not make a difference. Maybe to the contrary, higher temps should hasten fruit ripening.

I've had the same problem in the field - I think cooler temps and less sun (even if not a lot of rain) will delay ripening.

Another point is that, tomatoes can stay in green/growth stage for a LONG time(40 day ?). with large fruits it can even take longer. So, if there have bee new sets(late comers) , it will take them a while to grow and ripen.

And yet another point: In zone 5, CO, if the wether has been cooling off, it will slow down both growth and ripening.

The other point, already mentioned, is that if you fertilized with nitrogen rich stuff, the plant will concentrate on foiliage growth.
JMO.

i don't grow in a greenhouse,i live in northern alberta and my tomatoes are red and the plants are over 7 feet.no fertilizer,just rain