Weather in the Auvergne end of September?

Wunderground.com has hour-by-hour historical temperature graphs. Enter a suitable city name, choose Historical and Monthly, and look at Sept 2016, Sept 2015, Sept 2014, etc.

Many thanks, acraven. I hadn't come across that site; very helpful.

That's a wonderful trip.
A lot of the Auvergne is "en altitude", due to the mountains, though the train runs down a valley. However, I've run into sweater weather in July in Le Puy-en-Velay (en altitude), fog and mist hiking Auvergne in late May, and just threw in an extra sweater, windbreaker, and thin gloves for three days next to Clermont Ferrand the first weekend in September because Accuweather said lows of 40F/4.4C, highs in the 70s/21-26. But that's at a higher altitude than the train but three weeks earlier. So, to be on the safe side: windbreaker, wool sweater, neck scarf, and thin gloves if you get cold hands easily and warm jammies.

Thanks, Bets. Yes, I'm really looking forward to it. I was walking in the Cévennes at the end of May 2016 when it was much colder and wetter than usual, and wore all that you suggest. But that was with a group and we kept moving. I am what my grandmother used to call a 'cold morsel' (?mortal).
At least this time, after the initial week in mostly warmer places, I'll be free to decide how to spend each day depending on the weather, which one can't do with a group.

We did 8 days across Les Çausses Méjean and Le Cévennes beginning of April decades ago and it was warm and sunny most days that year. Just got lucky and as you say, moving with a group keeps you going and warm.

Not weather related but as an aside...you may enjoy listening to Songs of the Auvergne by Joseph Cantaloube. A collection of folk songs from the region. Beautiful! Have a great trip.

I am so glad you are visiting Auvergne! I love Auvergne and not many people post about it here. I did the train trip you are mentioning many years ago and don't remember what time of year I did this. I certainly don't remember the weather. I have been in this area, and in the mountains in October and the weather was lovely. I was also in Issoire in late November and it snowed -- damp and chilly and definitely icky. You just never know. I travel with a light fleece and a rain jacket and umbrella (and rain pants if I'm hiking) and that usually works for me for all but winter travel.

Don't miss the Romanesque church in Issoire -- and if you can get to St. Nectaire or St Saturnin, you'll be in for a treat, but these churches may be more difficult to reach without a car. Hope you have a wonderful trip!

Denny - I do know those songs but it's decades since I heard them. Must listen again before I go

Eef: good to hear from someone who has done that train trip. I'll certainly visit church in Issoire - Romanesque churches are a key interest of mine - but I have only a day and a half in Issoire and unfortuantely no way of getting to St Nectaire or St Saturnin as I don't drive. Another time, maybe. I do wish there were Romanesque special interest tours in France.
I'm adding a wooly hat to the packing list, but hope to manage without the waterproof trousers this time as I'm not hiking except for those 4 days in Sousceyrac

cgichard--just rechecked next weekend's accuweather for the area of the Auvergne where we'll be, and it's now 10-degrees F warmer than a few days ago. The gloves and scarf will stay in Paris. So, one can't tell very well in advance.

Am I in Albi now, my second cold wet day here, not good for wandering round little old streets. Improvement is forecast but not till later in the week, and nights still much colder than usual.