That's a really tough question. I suppose there are a couple of potential ways to get some kind of direction on this.
A - Feedback.
I'm sure lots of members will jump in say I walked Route X in October and it was dry, or I walked Route Z in October and it was wet. Maybe someone who has walked lots of different routes at that time of year will chime in with a view. Hopefully that will provide some guidance.
B - Research
This is my 'over planner' coming to the fore.
I'd start by eliminating some routes with some simple criteria.
- Do you want to finish in Santiago?
- How far do you expect to walk in 2 weeks, therefore likely start points.
- What 'type' of route you want to walk. Busy, Social, Quiet, Remote.......
Maybe try to get it down to 3 or 4 routes?
Then I'd start to look at climate and historical weather data.
If ending in Santiago, one would expect most routes would have similar weather?
As they'll all be in a radius of 2 weeks walk from Santiago.
Where weather may play a greater role, will be in routes or sections of routes, that will not end in Santiago. That would open up routes in the South for example, which 'might' be drier at that time of year.
I kind of tackled a similar question from a different angle when planning my last Camino.
I knew the route I wanted to walk, the VdlP, but needed to research the best start date to avoid the the rain and the very hot periods. I managed to slot neatly between the two, more by luck than judgement I'm sure!