Where did that apostrophe come from ...?
Personally I would wait for a dry spell
Polite cough, followed by long pause .......
The weather model of the mountainous British west coast is pretty tied to the Atlantic, & changes pretty fast. Fronts pass. Cloud punctuated by clearances & flashing light. Sometimes it gets northerly for a day or two (can be crisp!), or even comes from the south. Long winter periods can come from the east, with sometimes bright sun above but a spread-out layer of continental murk hugging the land and sea.
I'm no weather nerd. Maybe you should have half a mind to the forecast and be prepared to take a chance. It's not just about photography - you will have a life experience, whatever happens.
1000m up, it's colder, it's windier. You could need gloves in August. Winter isn't frightening, but on mountains you need to be be prepared for what might be up there (even on the boring tourist path from Llanberis).
If you want to live, that is.
I'm damned sure that you don't have crampons & an ice axe (I'm not joking), but there will be mountain condition reports at Llanberis, Pen-y-Pass & on-line. Forget the national weather forecasts - they're just about whether you need an umbrella or not at ground level in Manchester or Bristol.
Go on, do it, have an adventure! Often I've gone for miles, spent physical effort, and not taken the camera from its bag. It's not about trophies - it's about being alive, and taking a chance.