Is there a better time of year to walk the Camino?
Having walked the Camino in the Spring, Summer and Autumn I can confirm that each season comes with pros and cons. My favourite time of year to walk the Camino is in October, but that is a personal choice for various reasons. I have never walked in the winter as many of the hostels are closed, the weather can be rather miserable and you will certainly need to carry a lot more gear, but hey, if you are looking for some solitude then perhaps try walking from November to March, it may be exactly what you are looking for.
Listed below are the top considerations for the Camino Frances. What is important to you?
Walking in the best weather - October wins!
I have walked during the beginning of October, and also towards the end of October and the weather has been perfect. I experienced rain on the Pyrenees during October, but all other trips have been perfect. It is still rather warm, so I did not take a sleeping bag, just a silk sleep sheet which worked well.
Weather in Spring (March-early June) can be unpredictable. I have walked in May on three occasions now and experienced cold, wet weather twice, and sweltering weather once.
Weather in Summer is just silly. I would only recommend walking in the summer months if you have no other time in the year available. You will find that most pilgrims are waking up at 4.30am so that they can get to their next hostel before the mid-day sun makes an appearance. If sleep is important to you, then it may be best to avoid the months of July - September.
Please bear in mind that the Pyrenees section can still have snow on the mountains during the spring months, so it is worth checking with the Pilgrims Office in St Jean Pied De Port as to the current weather situation and asking their advice.
Having the lightest pack - Summer wins.
If what you are carrying is important to you, then consider walking in the summer. During the summer you are able to shed lots of weight. There is no need to carry too many clothes, you can leave your sleeping bag at home, perhaps even your micro towel (just use a sarong). You will unlikely use those waterproof socks and the list goes on. Carrying less certainly makes your journey more enjoyable.
If a variety of accommodation is important to you - Spring or Autumn.
From May to mid-June or end of Sept to mid-Oct, the Camino Frances route is busy, but there are still plenty of beds if you enjoy staying in the Albergues. In addition, there are many private B&B's or guesthouses available that are open at this time of year. During the winter months (sometimes as late as April), quite a few of the hostels are closed.
During the summer months, the hostels are all open but the volume of people creates the "race for beds" that we tend to hear about. In my experience, I have never not found a bed, especially if you are happy to upgrade on occasion. If you like to know that you have accommodation readily available then consider walking in spring or autumn, or simply pre-book your bed for peace of mind.
Try to avoid Spanish public holidays
It is wise to avoid 25th July (the Feast of St James) and the weeks running up to this event and a week or so afterwards. Most Spanish towns and villages will be partying into the night to celebrate this occasion, and the Spanish know how to party!
Also 15th August is a well known Spanish holiday (the Assumption of Mary) which is best to avoid, as is the Easter break (mainly due to overcrowding and heightened flight prices!).
There is a well-known phrase "there is no such thing as bad weather, just bad clothing". As long as you are prepared for your journey with the right gear, an up to date guidebook (or app) and the right attitude then you will have an awesome experience irrelevant to the conditions. Sometimes you just need to go with the flow and see where the road takes you.