Late October

We went the second week of October in 2024. We started with the north because we thought we would have better weather that way. We had rain one day in Porto, most of the time we were in the Douro valley, and one day in Coimbra. It was only 4 days of rain out of a 14 day trip but I have to tell you it seemed like a lot. It was hard rain and a bit miserable frankly. Our trip to Douro valley was a total washout.

We had beautiful weather in the Algarve and Lisbon.

The north is rainy in October. You have to be prepared for that.

We were just in Porto and Lisbon late this last October and early November and we had a small amount of rain in each location, but nothing that interfered with what we did each day. I thought it was a great time to be there.

We’re there in late September 2023 and had only one day that was a partial wash out. That was in Coimbra, so we just did laundry while it rained and walked around later. Otherwise, there was very little rain.

Wikipedia has climate-summary charts in its listings for cities. I like more detail than monthly averages for temperatures, but I use the Wikipedia charts for research on precipitation. Follow the link below and you will see how massively the rainfall rate increases from September to October--and November is even wetter than October.

https://en.wikipedia.org/wiki/Porto

There's no telling what you will actually experience; you might conceivably have one sunny day after another. But you should be prepared for a significant amount of rain.