What to expect in 100 mile wilderness in August?

You will get a lot of mixed opinions on the shelters. I can tell you that:
There will be mice. Guaranteed. They are fast and need about 10 seconds to chew through your pack and into your food. Some folks leave all of their pockets unzipped so they can inspect the pack without chewing a hole.
Most I have been in aren't trashy, just scribbled all over mostly. You can tell humans have been there.
If people snoring bothers you, set up a tent.

Ryan

Your trip falls right smack during hurricane season. It will be hit or miss in regard to rain. Here's a pic at Chairback Gap during Hurricane Ophelia:

There are no bridges over the river crossing so you need to remain aware and cautious during heavy rains.

The good news is that bugs really won't be an issue. Most of the bogs are crossed on boards. Here:s a pic of the bog on Fourth Mt in the Barren Chairback Range:

Temperatures should be 50s at night and 70s during the day. Don't try to over think it. I made the mistake of looking up weather on the AT before my trip and wound up over packing for cold.

The climbs aren't too much different from the Whites, but the first 15 miles from Monson is deceiving – the topos make it look like a level walk in the park. It's not, it's 15 miles of climb 200-300 feet only to lose elevation, constantly up and down. Nothing impossible, you just need to keep your head in the right place.

The Maine woods are gorgeous, but hardly a wilderness. I love it up there, so I am jealous. Enjoy and don't forget to come back with a TR and pics.

George and Ryan, thanks for the insights. George, that trip in the middle of Ophelia looks pretty miserable! Those temps are very reasonable.

Are there any parts of the trail that are overgrown that would make you want to hike in pants rather than shorts?

Can we get away with Driducks in lieu of dedicated raingear?

I'm hoping that I'm not overestimating our abilities to do the distance, especially on the first 2 days NOBO. I'll be taking extra food so if it takes longer it'll be fine.

Stay informed about the rainfall. Rivers become impassable after heavy rain.

Stay flexible, you might have to wait for water levels to drop.

Bring DEET

Be prepared to get wet

"Stay informed about the rainfall. Rivers become impassable after heavy rain."

How do people normally track weather conditions while on the trail? Rely on the last 10-day forecast? Fire up your smartphone on a peak and check weather.com? Ask other hikers? Or carry a weather radio?

We're planning on staying in Birches in Baxter SP. How likely is this to be full on Saturday, 8/24?

Sorry Curtis, I don't have any experience with dri ducks. As far as long pants go, the trail won't be overgrown. There are plenty of people up there in the "wilderness" so it doesn't get much chance to grow over.

Ophelia wasn't bad, but the trail looked like a river. I don't mind severe weather so I just went with it and had fun.

It depends on your conditioning as to how tough your itinerary will be. When I was in my prime 15-20 mile days in Maine were no issue. Not something I would even plan for today. I would say you'll know after the first day.

As far as the Birches go, it's hit or miss, although I would guess the odds are you'll be lucky to get space. Make sure you let the ranger know you thru'd the 100 when you call from Abol. Good luck.