Just check weather forecast before you leave & adjust your route accordingly. Look on Meteo France website. 14day forecast for that route is saying temps staying well up.
Can't remember where I found it but there is a site with web cam views of most of the main motorways in France.
We are just outside Madrid today and it is the warmest place in Spain at 63 deg F When we were in Granada at the w/e it was 70Deg and there was very little snow on the Sierra Nevada - they have been sending Spanish school ski parties home due to lack of snow.
We have been in Avila today which is usually bitterly cold and windy, but it was lovely.
The 14 day forecast doesn't give any temps below freezing.
There was no snow at all on the Sierras around Madrid.
We are taking advantage of the mild weather and seeing places in the mid/north of Spain, and using roads that we would not usually consider. It's great!
Don't forget to leave a review of the French and other European campsites you have visited!
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.