It is likely to be (will be) foggy along the coast, but this is atmospheric or romantic, not negative.

Inland, it is perhaps early for black flies unless it is a pretty warm spring, but trails may be muddy, and some trees, particularly at elevation, won't have their leaves yet. There may be spring skiing still, certainly just over the border in NH if not in Bethel.

Your main problem (sorry, I just saw the pun) is that a lot of eating places, particularly lobster pounds, won't be open before Memorial Day. But in your place, I would go in a minute.

The black flies are not as bad along the coast, but inland they are terrible. I had pigtails as a little girl and they always went for the spot behind my ears so I couldn't sleep on either side without a lump and that terrible itchy/hurt.

Maine is a fairly big state, and it's coastline is actually longer than California's. You need to decide where you want to be. Late May can be pleasant on the coast with temps in the 60's and even 70's, but is definitely not swimming weather - the ocean is sometimes bearable in the summer. The southernmost coast is the 'beachy' area, with long stretches of white sand beach, lots of touristy attractions, and some scenic lighthouses and rockbound stretches. The middle section is very scenic, rocky, with many charming coastal villages and a few small beaches. The northern coast is less traveled, more rustic and rugged.
As with any north country habitat, black flies are out in great numbers in May in woodsy fresh water areas.

Thanks for all the great info! I think we would tend to stay near the coast (no oceans at home!) and nobody in our group will care if they can go swimming (or not).

Would the area around Bar Harbor be a good choice?

Which airport is most convenient to the area?

I think you should fly into Portland, a lovely city with lots of good places to eat. Spend the first night there, maybe take the mailboat to the islands if you get in early enough.

Next day, drive up the coast to Bar Harbor. The road itself is not scenic since it does not go right along the coast.

Here are some places that are interesting or scenic along the way. You could catch them all on the way up, all on the way back, or split them between the two legs of the trip.

Freeport (LL Bean headquarters and lots of other shopping)

Brunswick (college town with good restaurants, gateway to scenic Harpswell and Bailey's and Orr's Islands)

Wiscasset (rich shipping town in 19th century, great architecture)

Boothbay Harbor (everybody's favorite tourist town)

Rockland (superb Farnsworth Museum of Maine art, lots of Wyeths, good places to eat)

Rockport is a tiny harbor/town on the back road from Rockland to Camden.

Camden (scenic harbor, windjammer cruises, views from mountain at state park just north of town)

There are wonderful back roads between Wiscasset and Rockland to places like Friendship and Port Clyde. Get a DeLorme Maine Atlas in Portland to find places like this.

Or you could fly into Bangor (one hour away from Bar Harbor) and out of Portland, or vice versa. I like doing open jaw tickets when possible so I only make a long drive one way.

Thanks for the good info! I will check fares into Portland and Bangor. I looked at Boston yesterday.

If we were going to rent a house is Bar Harbor a good base for exploring for a week? Any other suggestions? As I mentioned before, I would like to be near the ocean.

You might want to check Manchester NH for flights too. Southwest services it as well as other lines.

I love Bar Harbor and Acadia and think it would be a great place to base for a week. I have done so twice, and its wonderful.

I should have mentioned that only Delta and U.S. Airways fly to Bangor, except for a small amount of Allegiant flights.

My only time in Maine in May had terrible black flies. It was inland

We would never visit Maine in late May again. Black flies, mosquitoes, chilly rainy weather almost daily, restaurants still closed for the season, and hotels with summer-break college students who don't know how to clean a room or serve a meal yet.
Stick to Ogunquit and you might be okay, if the weather co-operates. But you're missing all the lakes and mountains that make Maine a special place to visit. Eat a lot of garlic and bring the heavyduty bug spray. Don't plan on any outdoor dining and choose a rental home with good new screens on the windows and a screened porch. Tape up any holes in those screens when you arrive.

Thanks for your honesty, clark! Were the flies bad even along the coast? If we went, we would stay near the ocean, although I totally understand what you are saying about missing the lakes and mountains. It's a real quandary.

With 5 people (ages?) and a week, I'd pick one spot - Midcoast, maybe (Ackislander has good ideas!) - and find a VRBO or other cottage rental. There are a good number of options and May is pre-season so the rent would be cheaper. Assuming you're flying in, you might want to find a place that provides sheets and towels so you don't have to schlep them on the plane (some rentals do, some don't).

People make it sound like *nothing* is open in May, but that's not really true. There are a number of things to fill a week just in the area between Portland and Rockland, and since it's not Summer, traffic up and down the coast and in all of those scenic towns will be reasonable.

If you aren't planning on a lot of hiking and biking, I think mid-coast would be a better choice for all the reasons Ackislander gives. Some of the places like lobster shacks might not be open until Memorial Day but there is plenty of other things open. There are at least three wineries in the Rockland/Camden area you can visit. Owls Head Transportation Museum has extra events on weekends. There's the Maritime Museum in Bath. There are several hiking areas in the Harpswells on conservation land. You can get a list. If the black flies are out, hiking the Giant Steps along the water might be fine. Going thru the woods on another property might not be. If we have a cold May, they might not be out and generally are only a problem in the woods. However, since I live in NH and eat plenty of garlic, I'm not usually bothered. They can be really bad one day and not so bad the next. If you aren't planning on a lot of hiking, they might not be a problem at all.