Hello khizr.
Well I'm happy your going on your Camino. I know it's going to be a blast for ya'. I'm planning to walk the VdlP roughly the same time you are. I'm planning to be starting from Seville on October 3. I do not mean to question your planning, but to me, your gonna be going a touch slow. I don't know your circumstances as to why, but I'm planning to do the same streach your doing in 17-18 days.
To answer your question about the weather. Everything I've read it seems that we should expect upper 70°f during the days and low to mid 50s at night. That being said, it is weather. I am going to be taking my raincoat and pants. Not so much for the rain, but for the wind. It can get pretty chilly up in those mountains. I walked the
Camino Frances March-April 2012. Was chilly!! I'm not planning for a lot of rain. But I'll still have my gear. I have a light cuccoon type sleeping bag I think will serve me ok.
I don't know if this is your first Camino or hiker, but if it is, really really think about what your taking. I saw all these people running around with 40-65 liter backpacks. Yes 65 liter bag!!! I had the smallest one at 26 liters and am really thinking about going down to a 20 liter backpack!!