Why does Helldivers 2 drop to 45 FPS during cloud physics calculations?

Crossing cloud layers in Helldivers 2 caused a massive FPS drop from 110 to 45. My ASRock B450M-HDV was suffering from E-Core bottlenecks due to heat. I tried Windows Performance mode, but it didn't help. I used the GamePP Fan Curve Configuration Panel to raise fan speed from 1200 to 1800 RPM and lowered the threshold to 68℃. Cinebench R23 scores improved from 32000 to 33500 points. Temps dropped to 78℃, and I exported the config as a backup.