Train ticket Prices

Maybe too far in advance to buy given the way airlines change flight schedules and September is 4 months away.
But if you buy a refundable ticket or the price is so low that you can afford to lose a non-refundable one go for it.

Jazz - Thank you had not thought of that, but I added a question.

I once gambled and bought a ticket from Gare de Lyon to Lyon Part Dieu a few weeks in advance that was dependent on my flight to CDG arriving on time.

It is always a gamble to try to buy one from the airport for the day your flight may or may not arrive on time.
I imagine most who buy these are business travelers that pay more for tickets that are refundable in case they miss the train and not leisure travelers.

Jazz, again thank you. I do not see an option to purchase a refundable ticket, that might be a great compromise!

I just found this post from 2019

"All TGV tickets (not Ouigo) are refundable now, as of May 2019. The fee on the day or the day before departure is 15 euro for standard tickets, and there is no fee for business tickets but those are more expensive. Cancellation deadline is thirty minutes before departure for standard tickets, and I think two hours after departure for business tickets (or maybe only one)."

Is this True? Do not understand "fee" Is that a extra fee for refundable?

Text copied from the SNCF Connect website:

Cancellation/Change Rules for TGV other than First Class--Business Premiere:

Ticket can be only exchanged (adjustment to the current fare) and refunded prior to departure: a charge of € 19 from 6 days prior to departure. From 30 minutes prior to departure, tickets can be exchanged up to two times (for the same day and the same journey), and are non-refundable after the first exchange.

Cancellation/Change Rules for TGV First Class--Business Premiere

Exchange and refund free of charge up to 30 minutes after departure. From 30 minutes prior to departure, tickets can be exchanged up to two times (for the same day and the same journey), and are non-refundable after the first exchange. To take a different train, it must be exchanged.

Cancellation/Change Rules for Ouigo:

Non-cancellable, non-refundable ticket. Exchangeable or modifiable online, subject to conditions, with an exchange fee of maximum 19€ per journey and per passenger, up to 30 minutes before your train's departure. Any difference in price between the old and the new ticket will be added to this fee. In addition to these costs, there may be a difference in fare between the old and new ticket. All changes are applied per trip and per passenger. The ticket is available starting from 4 days before the train's departure. Boarding is open 30 minutes before the train's departure, and access to the train is denied 5 minutes before departure. Proof of ID must be shown.

First Class Business Premiere is vastly more expensive than the other options, at least when you buy your ticket early. I'd consider it cost-prohibitive.

To see this sort of information you need to click on one of the fare boxes on the screen listing your departure options, then on Show details and finally on Pricing details, exchange and cancellation terms and conditions.

I'll be in France almost all of semptember.
I already bought all my train tickets using the SNCF app.
The ones after landing there are 3 to 4 hours after the expected time of arrival today.
They are now very cheap but using the app I've been playing slecting days close to today and they are expensive.
Your risk but for me it works!

Cheers!