I walked from Le Puy to Santiago and started in early September. It was 2015 and it was hot and that was before the recent and probably not ending anytime, disastrous and life threatening heat waves that Europe and especially the Iberian peninsula is experiencing. From what I read here September is not any better. I used to start my caminos towards the end of September. Now I start them in mid to late October. Yes there is rain and it gets colder. But you can always put on extra layers if it is cold. I have walked in December and on most days in Galicia I know to just wear a couple of outer layers because I know within a few mnutes I warm up. Yes it does rain. Last November when I did my final leg of my camino on the coastal CP it was raining hard, I mean really hard much of every day. I will take my chances in cold and wet weather any time over extreme heat, getting up to walk at 4:30 or 5:00AM and having to carry 2 or 3 liters of water.
This year, after reading some posts from
@C clearly and
@peregrina2000 I was about to change my plans and do the Mozarabe and then walk the coastal CP again (It was beautiful and peaceful) hoping that maybe the rain will not be anywhere near as intense. But because of family circumstances I would have to start from Almeria about October 10. So NO WAY is that going to happen. I am back to my original plan of doing the Aragones again, The Madrid and then another Coastal CP.
I just think between the heat and the risk of extreme heat, especially at my age (70) and especially because I walk caminos that do not see many other pilgrims or people, for me and my heat tolerance, no way!
I walked the VDLP starting about OCtober 20th from Sevilla a few years ago. It was 90+F every day for about 8 days. No shade (I would imagine you would be on the Meseta in very early October), and the sun beating down on me relentlessly, it was intense, to say the least.
You have heard all the arguments pro and con. You have to decide.
Other musings. I doubt very much you will find any air conditioning in the Gites. Could be really hot at night, especially sleeping with others. The same could be said and probably worse in the much larger rooms of albergues. Although I am sure there are some private albergues that have A/C on the CF. But I do not have any idea if they cool the rooms well enough. Others can answer this question.
Finally if any of us could predict the weather we would be multimillionaires breaking the bank in Sports Booking rooms in Las Vegas.