Which herbs are you interested in?

Last frost date to first frost date is your growing season. For me in western NY State that means late May - late September/Early October. Obviously some years vary. Our killing frost was very late this year but then again our frosts lasted late in the spring. You can google search these dates up for CT.

But Flora is very correct. Some herbs like basil HATE cool temperatures while others like cilantro prefer them. Timing is very plant dependent.

FataMorgana

And some evergreen herbs can be used year round in suitable climates. For me that's perennials like rosemary, bay, etc.(trees/shrubs), parsley (biennial) and fennel (herbaceous perennial).