Evergreen trees have needles, instead of flat leaves, to survive winter hardship.
The long, slender shape reduces the leaf area which, in turn, reduces the amount of water vapor escaping the leaf. Fahrenheit much of the time. About 20 inches of annual rain does the trick although trees can get by with less rainfall where it is cooler and evaporation rates are less. Evergreens can cope with much less water than broadleaf trees. In the mountains, you can identify zones where the different trees can live.