Major FPS spikes in rain maps

So normally in POE i get a 30-60 fps fluctuation with my system which is perfectly playable and i can still enjoy the game just fine.

Now the problem is when i enter any map with the rain weather effect on, it creates insane fps spikes and I end up going between 0 fps and 60...

Here's a screenshot of me entering the Colonnade map and even after 5 minutes idle in the spawn I am still getting these fps spikes:



This fps graph is a joke, and i dunno whats going on. I'm running the game with mainly low settings, vsync off (when thats on i seem to get 30fps more than 60fps, than i do with it off) shadows on low , antialiasing off and texture qual medium. I've got a dual core cpu which i guess is the culprit, but I know some ppl have no problem with rain maps and are running dual cores... Any ideas ?

Thanks

damn still no reply :(