Bretislav Stec

I can confirm this from my Skyblock world. I've attached log messages, there is some garbage because I've set CompileTreshold to ridicilous values, so don't get distracted by that.

http://pastebin.com/ig9MD5vA

So I did more investigation, btw. the issues I mentoined above occured after generating new world right after installing the new snapshot. However; the problem did not disappear, after more testing I found out that it is happening more severely in plains biome, probably because of all the grass and other 2D stuff. When I turned rain on, all the blocks suddendly stopped moving ( I made a clock with 16 repeaters and 1tick piston clock).
In the desert the rendering was in sync. I couldn't observe rain impact though, because rain in the desert simply doesn't happen.

Best to reproduce on a single-core CPU with weak GPU.

Edit: I've tried it once more in an rainy non-grassy biome and I hit the same issue when it was raining - all the pistons and repeaters stopped, I could trace the redstone signal only thanks to particles ( also rain dropped my fps by 45%).

This still affects 14w31a. The updates may take tens of seconds on my Intel GM965 (everything on low). TNT craters seems to be re-rendered relatively quickly (often less than 7 seconds).

This is actually a duplicate of MC-62166

I can confirm this. The updates may take tens of seconds on Intel GM965 (everything on low). This is happening with every block in the world, but TNT craters seems to be re-rendered relatively quickly (often less than 7 seconds).

Added screenshots (The first two are describing the bug, the third is a workaround)