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This paper describes the diversity of climatic and microclimatic conditions at cactus habitats in Chile. In the high Andean meadow of northern Chile Opuntia ignescens is exposed to cold temperature almost every night and therefore prefers sites with some microclimatic advantage. In the pre-Cordillera in the north there are dense cactus communities (e.g., Oreocereus, Corryocactus) limited by cold night temperature towards the east and by aridity towards the west. Browningia candelaris can be found in erosion valleys with precipitation-runoff from the Andes as the most important water-source. All these sites belong to the tropics, with rain occurring in summer. The Atacama Desert separates these tropical habitats from areas of Mediterranean winter precipitation. In the north, Copiapoa and Eulychnia, amongst others, live in the coastal mountains, strongly influenced by winter fog. This fog rarely condenses on the plant-surface but can be taken up by the roots after condensation at the soil-surface. Further south, species of Echinopsis and other genera ape sustained by winter rain. Maihuenia poeppigii, in southern Chile, lives in a highly humid environment, while Austrocactus is at sites with continental influence. Along coastal southern Chile no cacti can be found. Some information about the soil environment of Chilean Cactaceae is also given.