A microclimate is a region or space that has a different climate than the area around it. Microclimates are both large and small. They can extent for miles and occur within a garden. A microclimate can be warmer or cooler and wetter or drier than its environs. Geography and topography are the main causes of microclimates. Large bodies of water cool the air and make it damp. Wind dries up the soil on exposed mountaintops. Concrete, brick and asphalt absorb the sun's energy and heat up the atmosphere. Tall buildings create shadows and channel wind making streets cooler than the air above. Valleys are cooler than hillsides on winter nights as lighter warm air rises and heavier cool air falls. The south face of a mountain is warmer than the north as it gets more sunlight. (In the Southern Hemisphere, the opposite is true.)