Weather, Climate and the Controls of Climate Zones

Weather is the state of the atmosphere over hours or days, while climate is the typical pattern over decades, usually averaged over 30 years. Several controls explain why climates differ. Latitude matters most, because the Sun's rays strike the tropics more directly than the poles. Elevation cools the air by about 6. 5 degrees Celsius for every 1,000 metres, so mountain towns near the equator can be mild.

Ocean currents move heat: the Gulf Stream and North Atlantic Drift keep western Europe far milder than places at the same latitude in Canada. Distance from the sea creates continental climates with hot summers and very cold winters, and prevailing winds carry moisture or dryness. In the 1880s Wladimir Köppen classified climates using temperature and rainfall linked to vegetation, and his system, later refined with Rudolf Geiger, is still the standard way to map climate zones.