Fps at Sunset (The Witcher 3: Wild Hunt)

In general, the situation is as follows: at dusk (and dawn, i.e. around 10 pm and 8 am) FPS drops heavily in many places. Almost 2 times. In the forests, in the fields with a lot of vegetation, or, for example, in front of the house of the sorcerer in Vronnitsy. At any other time of the day 55-60 fps in these places, and at the indicated hours it sags as much as 30-35. Does everyone have such a problem? What is so special about the sunset that the FPS falls so sharply?

Iron - i7 3770, gtx 970, 8gb. Settings - everything on max except for drawing the grass (it is high) and hair smoothing (disabled at all).