An IWorld object represents the world the player is currently in.

It might be required for you to import the package if you encounter any issues, so better be safe than sorry and add the import.
import mods.contenttweaker.World;

ZenMethod	ZenGetter	Return type	Description
ZenMethod isRemote()	ZenGetter remote	Return type boolean	Description True if the world is a "slave" client; changes will not be saved or propagated from this world. For example, server worlds have this set to false, client worlds have this set to true.
ZenMethod isRaining()	ZenGetter raining	Return type boolean	Description Returns true if it is currently raining
ZenMethod isThundering()	ZenGetter thundering	Return type boolean	Description Returns true if it is currently thundering
ZenMethod getMoonPhase()	ZenGetter moonPhase	Return type int	Description Returns the current moon phase
ZenMethod isDayTime()	ZenGetter dayTime	Return type boolean	Description Checks if it is daytime
ZenMethod getWorldTime()	ZenGetter time	Return type long	Description Returns the world's time
ZenMethod getDimension()	ZenGetter dimension	Return type int	Description Returns the world's dimension
ZenMethod isSurfaceWorld()	ZenGetter surfaceWorld	Return type boolean	Description Returns whether you are in a surface world or not
ZenMethod getDimensionType()	ZenGetter dimensionType	Return type String	Description Returns the dimension's type name
ZenMethod getRandom()	ZenGetter random	Return type CTRandom	Description Returns the world's random number generator

• IBiome getBiome(IBlockPos blockPos);
• boolean setBlockState(ICTBlockState blockState, IBlockPos blockPos);
• ICTBlockState getBlockState(IBlockPos blockPos);