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Urban climate refers to climatic conditions in an urban area that differ from neighboring rural areas and are attributable to urban development. Urbanization tremendously changes the form of the landscape and also produces changes in an area's air.
Temperature
Main article: urban heat island
Urban areas tend to be significantly warmer than their rural (and possibly suburban) surroundings, particularly at night. As population centers grow in size from village to town to city, they tend to have a corresponding increase in average temperature (which is more often welcome in winter months than in summer). The U.S. EPA says: "On hot summer days, urban air can be 2-10°F hotter than the surrounding countryside." Not to be confused with global warming, scientists call this phenomenon the "urban heat island effect." [http://yosemite.epa.gov/oar/globalwarming.nsf/content/ActionsLocalHeatIslandEffect.html
Rainfall
Cities absorb much less water per square metre than rural areas, as much of them is paved or built on. In some areas this creates a need for specific measures to reduce the risk of localised flooding during periods of heavy rainfall. Measures include the use of rainwater storage and drainage systems. In some areas this may involve storm sewers to collect rainwater separately from household blackwater, to reduce the risk of polluted water overflowing during periods of rainfall heavy enough to overwhelm sewers.
Vegetation
According to one study, the growing season in east coast U.S. cities is fifteen days longer than in the surrounding rural areas. This is attributed to the higher temperature. *
See also
"Urban climate"