Where to "live" and work remotely for the month of September?

If it is your first trip to Spain, stick with your list, especially Madrid and/or Barcelona. But if this is a return, or you are looking for something more out of the mainstream, consider Valladolid and/or Zaragoza.

Hi Brad,

We do something similar every year or so. We spent December in Sevilla, then stayed for Christmas and went to Madrid for New Year.

We started in Granada for 3 nights so we could see the Alhambra. Then took a bus to Sevilla and lived in an apartment for 3 weeks. Then went onto Madrid.

There is a lot to see and do in Madrid and Sevilla. We’ve also been ti Barcelona and there is a lot to do there as well!

Madrid is a big city. It’s beautiful - reminded me of Paris! Lots of hustle and bustle like New York.

Sevilla is much smaller. Stunning! On a River. Lots of outdoor cafes, historic sights, an old pedestrian quarter. Approachable, not intimidating. All walkable but great bus and train service.

Here is my recent trip report for more detail: https://community.ricksteves.com/travel-forum/trip-reports/december-in-andalucia-spain

Best pricing deals would be staying one place for a month.
I haven't been to Barcelona, but Sevilla and Madrid have easy day trip access to a variety of offerings. I am sure Barcelona would too. Each city has a different vibe, but I expect all would be rewarding.
Spain has been hard hit with global warming, and this was a drought year. Add the energy conservation in place due to oil restrictions, AC may be limited, and water is precious. I think our regular here, Carlos, has published about the concerns of tourism on Spain's resources this year.
For actual temps, check historical weather data for each city last five Septembers. I expect all would be hot..in some degree. You would want to ask host before commitment whether central AC is guaranteed every day of the rental period.

Brad,

Logroño. Some reasons, ideas to think about....

a. it is not a super touristy place like those you've mentioned. Advantage, the rentals (and life in general) are cheaper than those places.
b. the weather is not (usually) as hot as some of the other places, and we usually have a rainy day or two for San Mateos.
c. San Mateos. This is the wine harvest festival around the 21st of the month. Unless you have an apartment in the center of the old town, you can work without much problem yet still participate in the festivities.
d. There is easy bus and train connections to Burgos, Bilbao, San Sebastian, Vitoria, Pamplona, Zaragoza, and Soria. Most are an hour or so away. There are also good regional buses that can take you to the villages like: Laguardia, Najera, St. Domingo de la Calzada, Haro, Calahorro, Estella.

Again it is not a famous place, more a back door. Just a suggestion,

Dave
PM if you'd like some more details.

You may want to check what the requirements are for remote working whilst in Spain. I know there is a digital nomad visa that allows you to work remotely in Spain but I don't know if there's a set period that you can work without requiring the visa.

Yes make sure you have the proper credentials and visa to work remotely from Spain, else you will be breaking the law.

Lucky for you Spain has recently introduced a digital nomad visa, for people like you to work remotely. You can apply for a digital nomad visa directly through a Spanish consulate or embassy in your home country.

If I had to live in Spain for a whole month, I might just pick a suburb or commuter suburb of Madrid.

Alcalá de Henares is a University town near Madrid and has a wonderful Old Town and you can be in Madrid via train in 35mins. It's also where the writer Cervantes lived.

I would choose Valencia without a second thought. Though perhaps it has fewer "big name" sights to see than the other cities you mention, it's exceptionally liveable, and it also has a very businesslike vibe (I assume you still need to do actual work, and I found internet access to be very speedy there). And the proximity to the shore, excellent food (it's the probable origin of paella), exercise and recreation opportunities and diversity of neighborhoods all recommend it highly, to me at least.

Wherever you go, enjoy your time in Spain!