> I often thought about making some kind of a clothes chooser website that took into account the temperature and a bunch of other factors.

I had a similar idea once upon a time, it'd take in your proposed route and what time you'd be at each point then look up the weather for each point and generate a "ride weather forecast" (since for 80-100 mile rides you can be out for 4-6 hours the weather in the UK can change on a dime) with appropriate clothing.

In the end it was just easier to look up the forecast for each area manually but it'd definitely be something I'd use if it existed.