October can be a really good time to go to Skye and the Northwest but yes, it is likely you will find it very changeable but when/if you do get the light (even fleetingly) its quality can be remarkable and it will make the colours in the landscape as it heads into autumn/winter all the more spectacular. You also have the possibility of the first dustings of snow on the higher mountains.
Personally, I would suggest you look at sights on the east of the island early in the day and on the west later-on/towards sunset, which makes the best use of the available light - Particularly the Trotternish Ridge which goes into deep shadow not long after the sun has passed its zenith, catch it in the very early morning when the low angle sunlight is right on it.
Normally it is also a time when you can expect visitor numbers to be low but Skye's recent elevation in status to a "Must See" destination has resulted in numbers remaining high all year now, so book everywhere well in advance, esp restraints/accommodation - Skye is often fully booked for months on end and COVID has meant reduced numbers in all places to eat etc, with some reduced to carry-out only.
The once renowned Three Chimneys has lost its chef - the jury is still very much out on the new guy is up to it but they still trade on their old rep and the prices don't seem to have gone down.
Get used to sitting in long slow queues of camper vans or finding them parked-up en-masse wherever you want to park. Apparently the numbers heading to Skye and the Northwest Highlands this year have been beyond the already unsustainable levels recorded over the last three years.
You can also expect that a great many of them have no clue whatsoever about the etiquette for driving single track roads and two great long nose to tail queues of vans meeting each other and struggling to get past on single tracks has become one of the "joys" of getting about the island - I've seen drivers break down in tears at the top of the Trotternish Loop when they find out the nearest two lane road back to Portree is still some miles away.
Despite being near-completely written-off by Visit Scotland under the current tourism policy, they were forced to release some money for improvements last year, so a number of the most popular sites have or are getting better access but there is still a way to go till the improvements are completed. This also means parking restrictions TROs etc and yes, they are being enforced.
Learn to shit in a plastic bag and take it away with you - Excrement has become a particular problem this year and Public toilets are few and far between at the best of times but a number have been unable to be made compliant with current guidelines so have not reopened, plus other places with toilets are not opening them to the general public any more.
Don't just stick to the "Must See" destinations. Skye is a large island and there are still thankfully plenty of absolutely lovely spots that don't see many visitors - esp down in Sleat.
Elgol and Loch Coruisk is also one of the most spectacular places you can see on Skye but the big numbers have yet to pick-up on it but the boats are still running and that helps limit numbers. So don't be afraid of taking-off down a road that has grass growing out of the middle of it!
