Massive Lag on Single Player world.

Since the update to the new snapshots for version 1.8 I have received massive lag for almost everything in my world. It feels almost identical to frame rate loss with millions of entities but I have 60 FPS and I have checked the entire world for high entity count. All chests have several seconds before opening, mobs are all frozen in place and take several seconds to react, portals have a delay before transporting, food takes longer to consume and etc. My world has about 100 of the older villagers at the spawn chunks but they have never caused trouble before this update. I do not understand why this lag is occurring hopefully it is just the snapshot and not the world. The rain on the world also never stops even after I enter a command to turn it off. The lag affects both creative and survival. After some testing on the world that had the problem I noticed that if I go back to version 1.7.4 that particular world refuses to load. Every time I click on it to load it begins to generate the world then returns to the home screen. I don't have this problem on any of my other worlds.