As mentioned in the Detailed Instructions document, there's no such thing as bad weather only the wrong clothing
That's why many LD riders wear waterproof textile gear, so you can just zip things up when it gets wet/cold instead of keep having to stop and put on/take off leggings and/or over suits.
Having said that during a couple of the early RBLR1000's we had horrendous driving rain for many hours heading north so an oversuit and even overboots came in handy over the top of my already gore-tex gear.