Which Portugal cities for a 22 night trip...by public transit

You can also fly non-stop from Amsterdam to Porto for as low as $52.
Sintra, Coimbra, Tomar and Aveiro are easy day trips from Lisbon by train:
Sintra (1h)
Coimbra (1h 30)
Tomar (2h)
Aveiro (2h)
In Lisbon I would sleep in the Alfama neighborhood. You can also see the Douro Valley in a day and sleep in Porto the whole time. I think you should make your home in two locations only. You won’t find much to do in the Algarve in Feb so skipping it is a good idea.

I wouldn't want to take day-trips to places 2 hours away.

I've been to Portugal twice, but that was long ago when I had somewhat limited vacation time and didn't do the sort of slow travel you (and I) now prefer. And I don't travel to Europe in the winter (average highs do not adequately convey how chilly it can be at 9 AM or 6 PM), so I don't have a strong basis for contributing thoughts here. However, I'm looking at those 3 nights in Coimbra and Aveiro, and thinking they might be too long unless you have side-trips planned. Aveiro isn't far from Porto; there's both bus and rail service, taking no more than 1-1/4 hours (according to Google Maps). Aside from reducing the number of hotel changes, I like the freedom of longer stays in fewer places when I have a list of potential day-trips to draw on. I can look at the weather forecast and try to suit my activities to the expected conditions each day.

I enjoyed the market (still on Thursday, I think) in Guimaraes, another town that is probably a viable day-trip from Porto; I'm guessing it's year-round but haven't verified that. There's also Braga, but I haven't been there.

Viseu's off the American-tourist route, but it's east of Aveiro so probably a bridge too far if one is staying in Porto and day-tripping to Aveiro. If you stick with the plan for 3 nights in Aveiro, you might read up on Viseu and see whether it would interest you.

Evora's beyond my usual day-trip limit. I'd try very hard to find an additional point of interest in that area (with bus service available) to justify 2 or 3 nights in that part of Portugal. I haven't been there myself, so I have no suggestions to contribute.

On my second trip to Portugal I took advantage of a bus tour from Lisbon that got me to several smaller towns north of the city in a single day. I know one stop was Batalha (for the abbey). Obidos may also have been included; it's a very touristy walled town in the summer. It might be dead in February, but the wall would still be there. Of course, such tours might not run frequently--or at all--in February. I don't know why I'm happy to spend so much time on a bus tour if it gets me to at least 3 small towns but am unwilling to do 4-hour round-trips to a single destination, but that's how I feel.

What I see missing from your mid-winter trip is the lovely island of Madeira, but it would require a flight from Amsterdam (if available) and back to the mainland. Madeira is drop-dead gorgeous and considerably warmer than Lisbon. A slow traveler could occupy herself for a week there, I think. There are great walking opportunities along the (flat) irrigation canals (levadas), and there's bus service to most of the places a tourist would want to go. Although Madeira is unlikely to be chilly at any time of the year, you're not guaranteed to have dry weather there, especially outside of summer.

While I've never been averse to off-season travel, I would say that particularly in the north, it could be cold and rainy. 50 doesn't sound bad until you're staying in a place with no heat. (Houses don’t necessarily have heat; most hotels do, though.) The dampness cuts right through you. While not as rainy, Lisbon isn't great either in winter. I'm not saying don't go, just be prepared. One thing to keep in mind is the necessity of good, sturdy, pavement-gripping shoes. The sidewalks can be really slippery in the rain, and the hills in both cities spell disaster for the less-than-sure-footed. And layers. A day that starts in the upper 40's low 50's will warm up, but you'll be glad to have that sweater in the morning.

You didn’t say where/when you planned to take your down days, so maybe my comments won’t help. Nevertheless….. Personally, I think 3 days in Aveiro is two too many. I was mostly working when I was there, but it's still kind of dull, especially in the evening and in February. There's plenty to see and do in Lisbon, but one of Lisbon's charms is walking around the different neighborhoods, so again, be prepared. I think 3 nights in Coimbra would be fine with day trips or a rest day. The nice part about being there in February is that the students will be there, which gives the town a whole different personality. Viseu is fine for a day or two, but I wouldn't even consider it in the winter. I think you'd be better off staying in Lisbon an extra day or two and going slow by doing leisurely full-day trips to Evora, Sintra, Belem etc. Or, spend a few days in Evora and from there day-trip to Arraiolos for carpets or Estremoz (for the market on Saturday) and there's a neat art museum housed in an old palace. But check what's going on in advance. Exhibits change pretty often, and sometimes there are lulls between the exhibitions. Both make nice day trips. But, I’m not sure how you’d do it with public transportation. I’m sure there are busses, but have no idea how many or when. There's a cool observatory in Monsaraz, but without private transport, I think getting there would be problematic. You'd also have to be stuck out there overnight. Failing public transportation, there are always guides with Tours by Locals or other organizations. There's plenty there to keep you busy in the region. Even in winter, cork farms are interesting.

Personally, I love Porto, but it is light on inside activities. There aren't a lot of museums, but the music scene there in the winter is pretty good. When we originally planned to go to Portugal in November, I wasn't able to find any Douro River cruises after November until the spring. It won't be pretty out there in November. Have fun. Even mid-winter, Portugal is wonderful.

After living here for five winters, I can speak a bit to the weather. February can be lovely with bright blue skies and temps in the low 60’s. Or it can be dark, rainy and high temps in the low 50’s (Lisbon area. Colder in the north). I personally like the winter for the most part because of the beautiful days that are (pre covid) days without tourists!

If you rent apartments (which I highly recommend for the longer stays) be certain to ask what kind of heat. Listings will say they have heat when there is nothing but a couple of oil radiators. I spent five nights in Porto in February and almost left the first night before the oil radiators had time to heat the place up. Porto was lovely but cold - temps hovering around freezing. It doesn’t freeze in the Lisbon area, but apartments with no heat still get quite cold. I don’t think you are spending too much time in either Lisbon or Porto.

Aveiro is not a place I would stay 3 nights. I have a trip planned there is September and am staying two nights only because I have an appointment for my residence renewal late in the afternoon one day.

Boats do not run on the Douro in the winter, but you might get one of the short ones that does the bridges around Porto. The day tours might still run but I’m not certain. They are quite nice as they take you to a couple of wineries and give you a taste of the Douro with a one hour cruise included on most.

In Coimbra, Go Walks does a very good walking tour that includes the university and library - a must see.

In Porto - Taste Porto does a great food tour.

While the Algarve can be lovely in winter, I, personally, don’t think you are missing anything to skip it. Some areas are quite dead out of season.

Thank you all for replying and addressing my questions. After considering the weather and my preferred activities, I have decided a visit in warmer weather will suit me better.

Your recommendations will help me plan that trip.

Becky

Others...feel free to weigh-in for the benefit of others considering a similar trip. :-)