Why does FPS drop from 90 to 40 in Crysis combat?

In jungle firefights, whenever explosions stacked up, my FPS plummeted from 90 to 40, which is absolutely lethal. I first tried limiting the max frame rate to 60 fps; the fluctuation decreased, but the overall smoothness dropped, making me desperate for a real fix. I activated the GamePP Power Plan Switcher to force Ultimate Performance mode and disabled core parking. GamePP Frame Time Analyzer confirmed a 10-13ms generation time, and AIDA64 showed stable temps at 78-82℃. Combat is finally fluid.