Lisbon for 3 to 4 days and winter; Porto for a long weekend

Porto is compact: one dramatic river centre, 2 to 3 days

August: 10.2 days above 30°C in Lisbon, only 3.5 in Porto

Porto gets 1,146.9 mm of rain a year, Lisbon 793.5 mm

Day trips: Sintra 40 min from Lisbon, the Douro valley 2 h from Porto

Lisbon has fado and ginjinha; Porto tastes port in Gaia's lodges

With a week, do both, 3 hours apart by train; sample week in guide