Isle of Skye without a car

Do you mean literally a one-day trip, sleeping in Edinburgh both before and after? I don't think you have enough time to do that. The train from Edinburgh to Fort William takes about 5 hours one way. There's usually a change of trains in Glasgow. Departures are at 4:50 AM, 7:15 AM, 11:15 AM and 5:15 PM.

I know you can find a one-day bus/van trip from Glasgow to the Highlands, but even from Glasgow you'll spend a great deal of the day sitting in the vehicle. The travel time is really significant. If you truly have just one day for an adventure outside Edinburgh, I'd check Rabbies to see what they offer. Their tours always seem to draw positive comments. However, even they cannot alter Scotland's geography.

The 0450 from Edinburgh is the Sleeper train from London and is compulsory reservation, as there is only one seating coach.
But from Fort William you have to catch a Citylink coach which leaves FW 3 minutes after the Coach arrives.
So you would be better off taking the 0435 coach from Edinburgh, changing at Glasgow. That arrives at Portree at 1305.
You would have 2 hours there before catching the 1540 coach back, arriving at Edinburgh at just about midnight, or change into the Sleeper at Fort William, arriving back very slightly later.
As a day trip that is brutal, and achieves almost nothing.
You need at least one night on Skye, two or three to make it worthwhile
But even then it is a full day each way. It's the same sort of script via Inverness.
A nice way to do it would be outward via the West Highland railway, return on Citylink to Kyle of Lochalsh, train to Inverness, then train Inverness to Edinburgh.
The Kyle line is another scenic spectacular.
The distance is about 250 miles each way, in difficult terrain, hence the long journey times.

Thanks, and sorry I wasn't clear. We are thinking about a 3-day trip, one day to get near Skye, one day to tour it, and one day to get back to Edinburgh. We're thinking about spending the night in Fort William or Inverness and getting a tour from one of those. I'm not familiar with the coach system, so perhaps we could take a coach from Fort William to Portree and sleep there? I've seen a number of day-tours out of Portree.

Phew,

Take the 0715 out of Edinburgh to Fort William, change to coach, which arrives at Portree at 5pm.

This is the Citylink website- https://www.citylink.co.uk/

Rabbies have a 3 day circular tour from Edinburgh, and you can ask them to find your accommodation- which, booking as late as May for August may be a very good idea. It is a pretty efficient use of your time, as you get to do things you couldn't just sat on the coach or train all day .- https://www.rabbies.com/en/scotland-tours/from-edinburgh/2-4-day-tours/the-isle-of-skye-3-day-tour

Hopefully skyegirl will have other ideas to throw in the pot.

One problem you're going to have is lodging. Portree is very popular, and finding a room for even one night there in August will not be a trivial task.

Also keep in mind the weather. That part of Scotland is extraordinarily rainy. With only one day in a location, you can easily find yourself rained out. Portree has an average of 17.6 rainy days in August. That doesn't mean it rains all day, of course, but I lost more than one day with planned outdoor activities to rain when I stayed in Oban and Portree in 2019. If you get soaked to the skin and the temperature is down in the 40s (F), you can be quite uncomfortable.

Hi,

isn31c has given you great advice. You will find it nigh on impossible to get accommodation on Skye in August on your own, so if you do a Rabbie's tour you can ask them to find your accommodation. But I'd get on the case now to be sure.

Another option to find accommodation would be the facebook group called Skye Rooms, which aims to match those seeking last minute accommodation with providers who have availability.

Good Luck!
Jacqui (Skyegirl)