Appendix C: Koppen Geiger Classification Descriptions

Group A: Tropical (megathermal) climates ^[1]

This type of climate has  an average temperature of 18 °C (64.4 °F) or higher every month of the year, with significant precipitation.

• Af = Tropical rainforest climate; average precipitation of at least 60 mm (2.4 in) in every month.
• Am = Tropical monsoon climate; driest month (which nearly always occurs at or soon after the “winter” solstice for that side of the equator) with precipitation less than 60 mm (2.4 in), but more than 4% the total annual precipitation.
• Aw or As = Tropical wet and dry or savanna climate; with the driest month having precipitation less than 60 mm (2.4 in) and less than 4% of the total annual precipitation.

Group B: Dry (arid and semiarid) climates

This type of climate is defined by little precipitation.

Multiply the average annual temperature in Celsius by 20, then add

(a) 280 if 70% or more of the total precipitation is in the spring and summer months (April–September in the Northern Hemisphere, or October–March in the Southern), or

(b) 140 if 30%–70% of the total precipitation is received during the spring and summer, or

(c) 0 if less than 30% of the total precipitation is received during the spring and summer.

If the annual precipitation (in millimeters) is less than 50% of this threshold, the classification is BW (arid: desert climate); if it is in the range of 50%–100% of the threshold, the classification is BS (semi-arid: steppe climate).

A third letter can be included to indicate temperature. Originally, h signified low-latitude climate (average annual temperature above 18 °C (64.4 °F)) while k signified middle-latitude climate (average annual temperature below 18 °C), but the more common practice today, especially in the United States, is to use h to mean the coldest month has an average temperature above 0 °C (32 °F), with k denoting that at least one month’s averages below 0 °C.

• BWh = Hot desert climate
• BWk = Cold desert climate
• BWn = Mild desert climate
• BSh = Hot semi-arid climate
• BSk = Cold semi-arid climate
• BSn = Mild semi-arid climate

Group C: Temperate (mesothermal) climates

This type of climate has the coldest month averaging between 0 °C (32 °F) and 18 °C (64.4 °F) and at least one month averaging above 10 °C (50 °F).

• Cfa = Humid subtropical climate; coldest month averaging above 0 °C (32 °F) and at least one month’s average temperature above 22 °C (71.6 °F) and at least four months averaging above 10 °C (50 °F). No significant precipitation difference between seasons . No dry months in the summer (neither abovementioned set of conditions fulfilled).
• Cfb = Temperate oceanic climate; coldest month averaging above 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). No significant precipitation difference between seasons (neither abovementioned set of conditions fulfilled).
• Cfc = Subpolar oceanic climate; coldest month averaging above 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). No significant precipitation difference between seasons (neither abovementioned set of conditions fulfilled).
• Cwa = Monsoon-influenced humid subtropical climate; coldest month averaging above 0 °C (32 °F) and at least one month’s average temperature above 22 °C (71.6 °F) and at least four months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation is received in the warmest six months).
• Cwb = Subtropical highland climate or temperate oceanic climate with dry winters; coldest month averaging above 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation received in the warmest six months).
• Cwc = Cold subtropical highland climate or subpolar oceanic climate with dry winters; coldest month averaging above 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation is received in the warmest six months).
• Csa = Hot-summer Mediterranean climate; coldest month averaging above 0 °C (32 °F) and at least one month’s average temperature above 22 °C (71.6 °F) and at least four months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).
• Csb = Warm-summer Mediterranean climate; coldest month averaging above 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).
• Csc = Cool-summer Mediterranean climate; coldest month averaging above 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).

Group D: Continental (microthermal) climates

This type of climate has at least one month averaging below 0 °C (32 °F) and at least one month averaging above 10 °C (50 °F).

• Dfa = Hot-summer humid continental climate; coldest month averaging below 0 °C (32 °F) and at least one month’s average temperature above 22 °C (71.6 °F) and at least four months averaging above 10 °C (50 °F). No significant precipitation difference between seasons (neither abovementioned set of conditions fulfilled).
• Dfb = Warm-summer humid continental climate; coldest month averaging below 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). No significant precipitation difference between seasons (neither abovementioned set of conditions fulfilled).
• Dfc = Subarctic climate; coldest month averaging below 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). No significant precipitation difference between seasons (neither abovementioned set of conditions fulfilled).
• Dfd = Extremely cold subarctic climate; coldest month averaging below −38 °C (−36.4 °F) and 1–3 months averaging above 10 °C (50 °F). No significant precipitation difference between seasons (neither abovementioned set of conditions fulfilled).
• Dwa = Monsoon-influenced hot-summer humid continental climate; coldest month averaging below 0 °C (32 °F) and at least one month’s average temperature above 22 °C (71.6 °F) and at least four months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation is received in the warmest six months).
• Dwb = Monsoon-influenced warm-summer humid continental climate; coldest month averaging below 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation is received in the warmest six months).
• Dwc = Monsoon-influenced subarctic climate; coldest month averaging below 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation is received in the warmest six months).
• Dwd = Monsoon-influenced extremely cold subarctic climate; coldest month averaging below −38 °C (−36.4 °F) and 1–3 months averaging above 10 °C (50 °F). At least ten times as much rain in the wettest month of summer as in the driest month of winter (an alternative definition is 70% or more of average annual precipitation is received in the warmest six months).
• Dsa = Hot, dry-summer continental climate; coldest month averaging below 0 °C (32 °F) and at least one month’s average temperature above 22 °C (71.6 °F) and at least four months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).
• Dsb = Warm, dry-summer continental climate; coldest month averaging below 0 °C (32 °F), all months with average temperatures below 22 °C (71.6 °F), and at least four months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).
• Dsc = dry-summer subarctic climate; coldest month averaging below 0 °C (32 °F) and 1–3 months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).
• Dsd = Extremely cold, dry-summer subarctic climate; coldest month averaging below −38 °C (−36.4 °F) and 1–3 months averaging above 10 °C (50 °F). At least three times as much precipitation in the wettest month of winter as in the driest month of summer, and driest month of summer receives less than 30 mm (1.2 in).

Group E: Polar and alpine (montane) climates

This type of climate has every month of the year with an average temperature below 10 °C (50 °F).

• ET = Mild tundra climate; all 12 months of the year with average temperatures between 0 °C (32 °F) and 10 °C (50 °F).
• ETf = Cold tundra climate; at least one month with an average temperature below 0 °C (32 °F).
• EF = Ice cap climate; eternal winter, with all 12 months of the year with average temperatures below 0 °C (32 °F).