Geography IA The Climatic Symbols of Köppen (1936) (Monthly temperatures in this table mean average monthly temperatures. The high sun, or summer, season for northern hemisphere stations is May-October; low sun, or winter, November-April) Symbol Name Definition Description Remarks A tropical coldest month over 18°C (64.4°F) no winter For A climates B dry evaporation exceeds precipitation too dry for growth of forests For C & D climates & dry humid test (chart #1) BS steppe) see chart #1 at end of table precipitation insufficient for forests; grass and open brush in- stead. Precipitation very low, vegetation very scanty. BW desert) mild winter C mesothermal coldest month between 18°C and -3°C (64.4°F & 26.6°F) and at least one month over 10°C (50°F) severe winter, snow cover or fro- zen ground for at least a month D microthermal coldest month below -3°(26.69F); at least one month over 10°C (50°F) no summer, no trees E polar no month over 10°C (50°F) warmerest month above freezing, some vegetation ET tundra warmest month between 0° & 10°C (32° & 50°F) EF frost no month above 0°C (32°F) perpetual frost, lifeless m transition monsoon w in precipitation, f in vegeta- tion, see chart #2 end of table dry in winter with high yearly rainfall and rain forest w low-sun dry see chart #2 at end of table dry in vinter, precipitation mainly in summer half year w winter dry driest month less than 3 cm. and rainiest summer month 10x precipi- tation of driest winter month