FPS Drops in Howling Abyss and Twisted Treeline

Well the title is pretty obvious, when I'm playing the maps "Howling Abyss" and "Twisted Treeline" I experience a lot of sudden FPS Drops that result in a negative game experience, because my game just freezes for five seconds. In Summoners Rift I don't seem to have this problem, my FPS there is around 40-50 and it stays that way. In the other two maps my average FPS is 30 and it drops to 4-7 every minute, or when I get into a big fight, probably because he has to calculate all those particles. I know this has mostly to do with my PC not being really strong and stuff, but it is kinda weird I don't have it in Summoners Rift, so I asked other people if they had it too. And yes other people experienced hard FPS lagg in the two maps. Now I love playing all the different modes, and I would prefer to keep playing them, but with these laggs make it really hard to still enjoy them. So I'm hoping if Riot could fix this, or if anyone has any tips on how to resolve this problem.

Thank you very much for reading/answering!