Visiting start of September

The hubby & I are debating visiting New England (arriving 7th Sept). We've been 5 times before but 4 of those times were in Oct for the foilage & once in May. We've found really cheap flights from Dublin for the start of Sept & are thinking about booking this for a cheap holiday, instead of our usual trip in Oct.

What is the weather generally like at the start of Sept? I've read that Maine can be quite rainy... just not sure what to pack weather wise.

We would be visiting Vermont - probably Berkshires or Scenic Route 100 to Stowe. North Conway area. Debating a couple of nights Bar Harbor & maybe some Acadia hikes ... is start of Sept good for Acadia? What about whale watching? Then we would probably do the coast of Maine - Boothbay, Portland, York Beach. We'll probably see Salem, Gloucester/ Rockport. Going to skip Boston as we've been loads. I'd also like to see Newport in Rhode Island. Will probably skip the Cape too. Will most shops & restaurants be open? I noticed mid Oct when we go a lot of places are closing for the season or closed. I love a gift ship so love stopping in all the little towns & going for some grub.

I guess I'm asking - yes or no for start of Sept?

Thanks in advance <3