Climate is the big picture of conditions resulting from the interaction of atmospheric air masses, oceans and continents as the earth rotates and receives solar radiation. Climate ultimately controls temperature cycles, humidity, wind direction and force, and frequency and type of precipitation. The driving force of climate is the different amounts of solar energy received by various locations and types of surfaces on the earth. Climate, and in the shorter term, weather, results from adjustments being made in an attempt to equalize and distribute the effects of solar radiation across the globe -- an equilibrium that can never be achieved.

Climatic zones of the world were first classified by Vladimir Koppen in 1918 and have been updated as new information became available. The basic world classifications may be found in any comprehensive World Atlas. They are a good starting point for understanding likely conditions for design.

Similar maps, generalized for use in gardening and planting, frequently appear in publications as "zones of hardiness" and "fall freeze" maps. These are very useful to making specific design decisions and planting schedules.



from: Organic Gardening Magazine Web Page


For purposes of permaculture very
broad climatic zones have been identified:

•TROPICAL: no month under 64 degrees (18°C) mean temperature and SUBTROPICAL with coolest months above freezing but below 64 degrees; frost free

•TEMPERATE: coldest months below freezing and warmest above 50 degrees (10°C) mean temperature to POLAR with warmest month below 50 degrees mean or in perpetual frost condition.

•ARID: mean rainfall 19.5 inches (50cm) or less to DESERT with mean rainfall of 10 inches (25cm) or less. Sub-humid is any area where evaporation exceeds precipitation. (Permaculture, pg. 107)

Microclimate is the specific climatic conditions that are existing on a site related to land forms, vegetation cover, solar orientation and water bodies. In the big picture, climate is dominant, but at the site level microclimate plays a large role in selection of plants and sites for building and gardens. Microclimatic conditions may vary significantly from the general patterns of regional climate. An on-site weather station can be used to monitor climatic parameters and provide specific useful information. Design adjustments are made to accommodate or modify conditions. Placement of wind breaks, use of slope orientation and terracing, water catchment and storage and creation of solar traps are some of the techniques used to modify microclimatic conditions on a site and extend growing seasons.