How can I prevent FPS drops from 120 to 48 during dense cloud physics in Expeditions: Rome?

The FPS drop during cloud crossings was a pain. I tried Performance mode, but it didn't help. I used GamePP BIOS Wizard to set Load Line to L3 and VCCSA to 1.25V. Cinebench R23 scores rose from 35800 to 37200. RTSS showed stable 95-110 FPS, fixing the bottleneck.