 On the colder temperate side of the line, the total flora is adapted to survive periods of variable length of low temperatures, whether as seeds in the case of the annuals or as perennial plants which can withstand the cold.Only the warmest Mediterranean climates with a biotemperature between 16°C to 18°C and 24°C are subtropical climates in Holdridge classification.During summer, regions of Mediterranean climate are strongly influenced by the subtropical ridge which keeps atmospheric conditions very dry with minimal cloud coverage.