Vegetation Shading

• Many topographic maps, including the widely used publications of the U.S. Geological Survey, indicate forest cover and other general vegetation types with shading. You therefore can extrapolate basic levels of rainfall: a landscape dominated by grasses suggests semi-aridity, for example.
  
  

Wetlands and Waterways

• The USGS topographic maps also reveal wetlands like swamps and marshes, which also suggest at least moderate precipitation. Ephemeral streams -- those that dry up part of the year -- are common in semi-arid and arid climates, and these maps distinguish these from year-round drainages.
  
  

Erosion

• The degree and nature of erosion of a given landscape, shown by topographic maps, reflects the climate. A density of V-shaped drainages dissecting a mountainous tract -- as in parts of Hawaii or the Pacific Northwest -- often reflects a relatively wet climate with vigorous stream-cutting.
  
  

Glaciers, Snowfields and Elevation

• The presence of glaciers or permanent snowfields on maps indicates areas that are colder and receive heavy snowfall. Elevation contours suggest climatic characteristics, too, as temperatures are cooler at higher elevations, hotter the closer to sea level -- or below -- you go.