October is the middle of the autumn window, and the autumn is the prime season here for a reason: the west swells out of the Atlantic are consistent again and the winds are predominantly favourable, which is the combination the rest of the year struggles to produce.
The water is still at 18°C, level with September and August, so the wetsuit is a 3/2 and the days are still long enough to surf twice. It is also when Nazaré starts, a little north of Peniche, and the swells that make that wave are the same ones filling every beach further south. The crowds are those of the shoulder season rather than the summer.

