Switzerland in late August/early September.

When planning a trip I always start with RS guidebook listed hotels to get a sense of places and prices. Then I check Booking.com for the same areas and prices. If you skulk for a month checking weekly you will see if there are any/many/lots of price changes/places selling out. Of course "selling out" on a site like Booking does not mean a sold out hotel, just a hotel that has limited how many of its options will be posted by a consolidator. I would never book in anything that couldn't be canceled if I was 8-9 months out, but some people want to book and forget. Skulking for a few months however can't hurt and can inform. I have also found in popular places many people book cancellable reservations early and a place will seem "sold out" but then someone cancels those reservations and I have snapped them up.

The best thing you can do is look at a booking site like Nick mentioned, or go to a local tourism site like this https://lauterbrunnen.swiss/en/discover/accommodation.html.

Lean into Sept as much as possible. It is slightly better than even late August.

I would think 8-9 months in advance is plenty of time to book hotels,
but maybe not?

You shouldn’t have any problems, but the only way to know for sure is to check hotel reservation calendars and see if your dates are available.

Book the hotels ASAP and then book your flight.

I would not look around for months when it comes to lodging in the BO. You’ll be able to find something, but I’d do your research and get everything ASAP. You’ll have slightly more availability early September than in August. The main issues you saw with waiting to book are availability of chalet apartments in small villages and the best/most popular hotels with best view rooms.

Wengen is a good central base for a first trip to the BO, so I’d recommend starting your search there.

My tentative itinerary is as follows:

Fly into Zurich and take a train to Montreux.
3-4 nights Montreux. I loved Annecy (despite the many people on the forum who don't), so I'm thinking I'll love Montreux.
3 nights Zermatt. This one I'm not sure about since I haven't researched it enough yet.
5-6 nights Wengen. This is where I'll settle with a longer base to explore the overall area, so I might want more space than a small hotel room.
3 nights Lucerne. I was here once before, but need more time to explore.
Fly out of Zurich.

I'll be solo so while I will definitely do lots of hikes and walks, I don't want to get too far away from populated areas. Maybe 3-4 miles or so max.

Does my itinerary sound okay? I'll admit, most of my ideas probably came from Carrie's trip reports. :)
I haven't researched the various SBB passes too much yet, but convenience matters a great deal to me, so I'm thinking the STP might be best since it seems to cover the most. Still, I've got time to figure that out. I may even splurge on first class this time.

I think I'd like a lake view in Montreux and Lucerne, and it sounds like finding lodging with a view of the Matterhorn is doable in Zermatt. I like outside space, so a small balcony or at least a window that opens to the view matters. I like a small breakfast of coffee and fruit in my room in the morning, so having breakfast included is not necessary, but a coffee maker or something to heat water in the room is and a small fridge for leftovers would be nice. I prefer carry on, so I'll probably do sink laundry most days in the room. Based on this criteria, can you offer lodging suggestions?

Unfortunately, I don't have much wiggle room with my dates, so I'll probably book my flights this week, then build my itinerary around it.

I can't tell you how much I appreciate the helpful advice I receive from this forum. It makes solo travel less intimidating to know that if I run into a problem, I can reach out and get solid answers.

I'll admit, most of my ideas probably came from Carrie's trip
reports. :)

I was going to say, this sounds like a great itinerary. :-)

I would definitely get the Swiss Travel Pass.

All my hotels last year had great views. You will have to specify room with a view when booking and will pay extra, but it's worth it.

I do prefer the view from Murren over Wengen, but Wengen is easier getting to and from. You'll have to decide which is a higher priority. Of course, since you'll be there a week, you could always split your time. It takes no time at all checking out and in and getting from Murren to Wengen.

I booked my flight. I have 16 nights from late August into September. I land in Zurich around 2pm and will take the train from there to Montreux. I booked a hotel for 4 nights in Montreux, but still have to book everything else. I will spend 3 nights in Lucerne at the end of the trip, so that leaves 9 nights for Zermatt and Wengen/Murren. I hope to get lodging settled pretty quickly so I can start focusing on sites I want to see/hikes I want to do and all the other fun stuff. I still need to determine which SBB pass is best for me too.

I normally do a lot more pre-planning and researching before I book something, so this is a little stressful, but when a window of time opened up, I wanted to grab it. I'm open to any suggestions and help you can offer!

We were there in September, and were told by multiple people that we would not need air conditioning in Lucerne at that time of year. NOT TRUE! Temps were in the mid to high 80's every day, so we were very happy that our hotel did have A/C. Once we were in Wengen there was no need for A/C. Just something to consider. We were fortunate enough to be in the BO for the Alpine Parade; quite the entertaining experience!

Travelbug79, I was considering a hotel in Lucerne that many people on the forum seem to like, but saw comments about it not having AC, so ended up booking an Airbnb apartment without a great view, but with AC specifically for the reason you mentioned.

Fans and open windows are a reasonable alternative if the hotel offers a fan per sleeping room or ideally 2. While you’re gone during the day, shut all the windows and close all curtains to keep the sun out. Then when you return in the evening open the windows and turn fans on. I also bring a small portable bedside travel fan with me everywhere and between all those things we survived 2 weeks on Lac Leman (Lake Geneva) with temps in the 90s one summer. In Switzerland it always cools down enough in the evening to do the above, even when you’re not up in the mountains. We’re up in Mürren all summer and pretty much keep the windows open 24/7 and are totally fine up there. Anyway, just to say that having AC isn’t a non negotiable if the hotel will offer you fans + you bring an additional bedside travel fan.

wanderweg, I think the problem with too hot/too cold is that it's an individual tolerance issue. For me, if it's on the cold side, I can bundle up and be okay, but if it's too hot, I'm miserable.

Anyway, I've got all my lodging booked and I'm happy with it. The apartment in Lucerne is clean and close to everything, so it's okay, especially since I booked some nice places in the other towns where I'll be staying. Now my focus is on sites and activities. I visited Mt Rigi when I was in Lucerne last time, but didn't make it to Mt Pilatus, so will probably try to go there this visit. I'll be in Montreux, Zermatt and Wengen as well. Are there particular hikes/walks or other things you recommend?

Yes, I definitely understand the tolerance issue. I have a very low tolerance for heat, which is why I posted the info for others who might be concerned about it. Years ago there was a major heatwave in the lower elevations of the alps (got up to over 100) while we were there and we weren’t prepared, which is how I learned to travel with my own fans, learn the phrases to ask lodging for fans, places to buy them when needed, as well as the tips for making a place with no AC manageable. AC isn’t always an option in places and even when you do find AC, Switzerland has very strict laws on its use. Places have to get special permits to have them in Switzerland, you aren’t allowed to set them below 75.2 degrees & often the hours of use are restricted, so it’s not like American AC where you can blast it at 66 degrees to do a major cool off. I’ve been in buildings with “AC” on a very hot day in Europe and if it’s 92 degrees outside the AC at 76 is better than outside, but it certainly doesn’t feel like walking into a building in the US where everything is kept at igloo :)

Anyway, to better help with hiking suggestions, it’s helpful to know your skill level/difficulty preferences. You can also look back through my posts where I’ve given tons of suggestions for the areas around Wengen. We spend our summers in Mürren & often take people out on hikes in the area, so happy to help where I can.

Now that you mention it, I'd forgotten that I do have a small personal fan that I purchased from Amazon that works surprisingly well. I'll have to pack it.

As far as hikes, I'll probably stick to easy to moderate since I'll be solo, so no rock scrambling or narrow ledges. If I did a hike with a guide who is familiar with the area, I might get a little more daring though. If it's a mountain, I would generally prefer transportation up, then hiking down when possible, and probably not more than 2-3 hours at one time. Planning this trip was a last minute decision due to a few things going on at home in the coming year, so I haven't had much time to research yet. Thankfully, there is lots of information about the area just on this forum in addition to the other forums and blogger articles etc..