Minecraft wiki entry for Biome, associated text: The adjusted temperature and adjusted rainfall values (recognized as AdjTemp and AdjRainfall in the code, respectively) are used when determining the biome color to select from the colormap. Treating the bottom-right corner of the colormap as Temperature = 0.0 and Rainfall = 0.0, the adjusted temperature increases to 1.0 along the X-axis, and the adjusted rainfall increases to 1.0 along the Y-axis. The values used to retrieve the colors are computed as follows: AdjTemp = clamp( Temperature, 0.0, 1.0 ) AdjRainfall = clamp( Rainfall, 0.0, 1.0 ) * AdjTemp "clamp" limits the range of the temperature and rainfall to 0.0-1.0. The clamped rainfall value is then multiplied by the 0.0-1.0 adjusted temperature value, bringing its value to be inside the lower left triangle. Some biomes' ranges are shown in the template above; the multiplication makes all the line segments point toward the lower right corner.