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Koppen created a classification system for climatological zones based on precipitation and types of flora, and the boundaries between these zones. The short-and-sweet version follows; for the whole thing, see the URL at the bottom of this article.

Tropical/Hot Climates

  • Af - Tropical/Hot - Temperature in all months averages greater than 64.4F; rainfall averages no less than 2.4 inches in any month.
  • Aw - Tropical wet/dry (winter) Savanna - Like Af, but more than 2 months have less than 2.4 inches of rainfall; there are distinct dry seasons (Winter) and wet seasons (Summer).
  • As - Tropical wet/dry (summer) Savanna - Like Af, but with a distinct dry season (Summer). (This climate is only present in parts of Brazil.)
  • Am - Tropical Monsoon - Like Af, but with a very intense wet season. Sometimes found as a transition between Af and Aw climates. Very short winter drought.

Arid/Semi-Arid Climates

  • BWh - Dry/arid, hot, low-latitude deserts - Temperature in all months averages greater than 64.4F; winters are low-intensity, and there is seldom frost. Evaporation exceeds precipitation, usually by a factor of at least 2.
  • BWk - Dry/arid, cool, middle-latitude deserts - Like BWh, except that mean average temperature is below 64.4F; winter temperatures dip below 32F (freezing).
  • BSh - Semi-arid, steppe, hot - Like BWh, evaporation usually exceeds precipitation by a factor of 2. Mean average temperature is greater than 64.4F. May border BWh climates.
  • BSk - Semi-arid, steppe, cool - Like BSh, except that mean average temperature is lower than 64.4F.

Subtropical Climates

  • Cwa - Humid subtropical, warm with distinctly dry winter - Average temperature of warmest month is above 72.2F; average temperature of coldest month is between 26.6F and 64.4F. Very dry winters; wettest summer month will see at least ten times more precipitation than the driest winter month.
  • Cfa - Humid subtropical, east coast regions - Like Cwa, except that rainfall is distributed evenly year-round.
  • Csa - Humid subtropical, Mediterranean - Generally warm; summer is particularly warm and dry. Coldest month's average temperature is between 26.6F and 64.4F. The driest summer month will see less than 1.56 inches of precipitation. The wettest winter month will see at least three times that much. Warmest month has temperature of at least 71.6F; at least 4 months will have temperatures of more than 50F.
  • Csb - Also humid subtropical, Mediterranean -Like Csa, except that it is cool, with a particularly cool and dry summer.
  • Cfb - Marine west coast, mild - Average temperature during all months is below 71.6F. At least 4 months have an average temperature above 50F. Average temperature of coldest month is between 26.6F and 64.4F. Rainfall is equally distributed throughout the year.
  • Cfc - Like Cfb, except that there are only 1-3 months a year with an average temperature above 50F.

Temperate Climates

  • Dfa - Humid continental hot summers; year-round precipitation - Average temperature of coldest month is not greater than 26.6F; average temperature of warmest month is greater than 50F.
  • Dwa - Humid continental hot summers; dry winters - Like Dfa, except that the winters are dry, and the summers are wet; the wettest summer month will see at least 10 times as much precipitation as the driest winter month.
  • Dfb - Humid continental mild summer; year-round precipitation - Like Dfa, except that there is no month in which the average temperature is greater than 71.6F.
  • Dwb - Humid continental mild summer; dry winters - Like Dfb, except that the wettest summer month will see at least 10 times as much precipitation as the driest winter month.
  • Dfc - Subarctic; cool summers and year-round precipitation - Average temperature of coldest month is not greater than 26.6F; average temperature of warmest month is greater than 50F; 1-3 months have average temperatures above 50F.
  • Dfd - Subarctic; cold winters; year-round precipitation - Like Dfc, except that the coldest month has average temperature not greater than -36.4F.
  • Dwc - Subarctic; cool summers; dry winters - Like Dfc, except that the wettest summer month will see over 10 times as much precipitation as the driest winter month.
  • Dwd - Subarctic; cold summers, dry winters - Like Dwc, except that there is no minimum of 1-3 months with average temperatures above 50F.

Polar Climates

  • ET - Tundra - Average temperature of warmest month is between 32F and 50F. Precipitation exceeds potential evaporation.
  • EF - Icecap - Like ET, except that average temperature of warmest month is not greater than 32F.

Highlands

  • H - Highland - Describes mountainous regions. On an average, temperature decreases by 3.6F per 1,000FT of increasing elevation. Temperature at a given elevation roughly equates to changes in Koppen zones based on latitude and elevation, except that seasons only exist in these zones if they also exist in nearby adjacent lowlands.

  • Abridged and paraphrased from http://www.utexas.edu/depts/grg/kimmel/GRG301K/grg301kkoppen.html

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