Start the attached repro mission (use a dedicated server!), after 5s you should have overcast skies, set with:
skipTime -24;
86400 setOvercast 1.0;
skipTime 24;
sleep 5;
simulWeatherSync;
Let it run for a few minutes (at least 5), there should be no freezes.
Open action menu and select "Start server weather change". When triggered, the server will execute:
900 setOverCast 0.0;
sleep 900;
900 setOverCast 1.0;
sleep 900;
900 setOverCast 0.0;
After a while (can take minutes too), for me this causes intermittent freezes every few seconds.
See http://forums.bistudio.com/showthread.php?174250-FPS-drop-with-Patch which seems to be linked.