Hi
@Nicarandy /
@Robert Long - welcome to the forums.
Here's a link to a site with good historical weather information. This specific link shows Porto in Sept. You can look up other communities along your route to see patterns there, too:
http://www.myweather2.com/Holiday-Destinations/Portugal/Porto/climate-profile.aspx?month=9
Regarding the different routes, the two main ones are the Central and the Coastal. The Central is the more commonly walked option. It follows a (mostly) inland route from Porto to Santiago. The Coastal route, as its name suggests, mostly follows close to the coast. A variant of the Coastal route, the
Senda Litoral, follows the coast even more than the Coastal route -- much of the
Litoral is on beaches and boardwalks. The
Litoral and Coastal follow identical routes for much of the way though.
The Central is better waymarked, though either option is generally easy to follow. The Coastal route is very exposed, so wind, rain, and sun are more of an issue.
Many people move back and forth between the two options -- there are a few convenient places to do this. A common option is to follow the
Litoral out of Porto up to Vila do Conde and then cross to the Central at Arcos / Rates.
Of course, you can also start your Portugués at Lisbon -- the Central / Coastal split only happens at Porto.