Pyrenees Advice Please

Not done that route mate, spent a few days in Pyrenees last June, temp then was over 30 deg C most days, in parts that were in constant shade up high there was still some snow, but not on any of the roads we went on.
As a side issue, Jaca is a lovely place for an overnight stop, very good bars and restaurants which seemed very cheap, would leave you a relaxed days ride for the ferry the following afternoon.

 

I did a very similar route about 12 yrs ago. If you have time (maybe an extra 5-6hrs) I would recommend a turn West before you get to the Border and head over the Col du Tourmalet, reputedly the toughest climb on the Tour de France, then head South uphill to Gavarnie and its spectacular circle.

It’s a dead end so you blat back and keep turning left on the major routes back into Spain and rejoin your original route.
In September it will be pretty warm but cooling into the evenings. The snow will be well above your head! Hotel Le Marbore in Gavarnie was my bunk for the night and quite pleasant for a quick overnighted.

 

You should be fine,think the snow's come November time.
Oradour-Sur-Glane is worth a visit,very moving.
Potes is worth it to,bit touristy,watch out for the Tapas,it's massive.

 

Went through on that road a few years ago, should have no problems. As SJ say's Jaca is a great place to stop over and when it rains, it bloody rains. Not sure if it is still there but there was a fantastic truck stop at Agen, well worth a stop.
Wessa

 

You’ll have no problems with snow Andy at that time of year.

The area of France that your riding through can be quite hot at that time of year.

 

No worries mate, you’ll be fine!

Just don’t forget your summer clothing!