Once you arrive at the village (after passing the church) the fps will drop massively in that area (happens on all platforms (PC & Consoles). due to the particles (rain, wind, etc) and the amount of NPCs (enemies) that are present at that moment. To fix this you have 3 options (Only PC):
1. Altabbing the game (game clears any unused asset in the vram giving you around 1gb free more vram whenever you alt+tab the game, this can be a good fix for people with 4,6 or even 8gb of vram depending on selected graphics settings)
2. Pausing the game (after pausing the game for 5 seconds the performance becomes stable)
3. Opening the case (if the 2nd solution doesn't works, you can try this as well)
Source from these issues (BenchmarKing & Digital Foundry): https://www.youtube.com/watch?v=uMHLeHN4kYg https://www.youtube.com/watch?v=eS3De-wiPfA