Performance drop at Sunset/Sunrise-DayNight cycle(UE4 4.20.1)

Hello,

my problem is I have a Day-Night System, at Sunset/Sunrise the Performance drops (up to 5ms)!

Is this Normal? The Directional Light (Sun) works fine at Day/Night but at Sunset/Sunrise the FPS drops.
The Sun is Casting long Shadown at Sunset/Sunrise, could this be the reason for it?

Thanks!

-eric

The case, where your light is parallel to the ground is expected to cost significantly more in regards to shadowcasting.
Adjust the cycle in a such way, to completely disable the sun, when it approaches horizon.