These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best. Chemical weathering occurs most readily in warm, humid climates. Physical weathering occurs most readily in cool, dry climates. A warm, wet climate will produce the highest rate of weathering. The warmer a climate is, the more types of vegetation it will have and the greater the rate of biological weathering. This happens because plants and bacteria grow and multiply faster in warmer temperatures. Lack of moisture in deserts and low temperatures in Polar Regions slow down chemical weathering. Moisture speeds up chemical weathering. Weathering occurs fastest in hot, wet climates. It occurs very slowly in hot and dry climates. Polar Regions have low annual precipitation, extremely cold temperatures, and no higher-order plants. Thus, the extent of chemical weathering in Polar Regions is generally thought to be negligible.