Is it normal for a wind of 8kn (described as "gentle breeze") to toss the plane around like a feather in a tornado?

At least on two separate occasions these "gentle breezes" have been causing insane turbulence with the planes bouncing several meters up and down without a break after getting a bit of altitude. The on-board speedometer is swinging wildly between 60 and 50 knots and the stall warning is constantly appearing. For the extremely stable B.E.2 that I'm currently flying this is a mild inconvenience but for Fokker E.III it meant I couldn't let go of the stick to wipe the sweat off my eyes without instantly rolling 90 degrees and/or entering a spin.

What is the strongest possible wind that won't cause the flights to be cancelled?

You can customize wind, especially the turbulence and wind gusting with Multimod:

The latest version 1.9.1 available here .
Wind speed is possible to tune with help of Mission Editor - Weather manager, if necessary.

Thanks JJJ65, I might end up doing that.

What I really find odd is that I'm pretty sure I have flown several missions at 8 kn wind where the wind effect has been much lesser with just an occasional bump here and there. The two missions I mentioned have been peculiar because the wind and turbulence has been insane through the entire flight. Are there a lot of variables other than the wind speed and direction that is displayed at the start of mission? At least for the B.E.2 missions the wind seemed to be weak below ~200 meters.