Rainfall

The Rainfall level of a region determines the amount of Nutrients which can be produced. A region can be arid, moderate or rainy, producing 0, 1, or 2 nutrients respectively. A farm increases the nutrient production by 1. In addition to coastal and tropical regions, the western (upwind) slopes of mountain ranges tend to be quite rainy, since warm moisture-laden air cools as it rises, and sheds its moisture as rainfall. You can take advantage of this phenomenon by raising hills to the east of your important bases. Conversely, areas east, or downwind of mountain ranges tend to be quite arid. Ocean squares produce 1 nutrient unless you cultivate a kelp farm, in which case they produce 3. Special Nutrient Resource squares produce two extra nutrients, and Monsoon Jungle squares produce a single extra nutrient.