Precipitation, mostly rains, has a huge impact on agriculture. For the growing all the plants need a smallest amount of water at least, and rain is still one of the most effective ways of watering despite the development of modern technologies. Too much or otherwise too little precipitation is bad and even harmful for agricultural plants. Drought can destroy the harvest and can increase erosion as well as the overly humid weather is able to trigger a growth of unfavorable fungi. Moreover, various kinds of plants demand different amounts of precipitation. For example, some succulent species require little water while tropical plants need hundreds of inches of rain a year just to maintain their living.
A fluctuation of precipitation amounts is quite substantial in continental climates. A fluctuation of month amounts is bigger than those of year. A considerable precipitation variation leads to situations when there is a precipitation lack during some years, and drought takes place thus forming the areas of unstable hydration. With a long absence of rains and at high temperatures the reserves of moisture in the soil dry out due to evaporation. A previous arid season brings a shortage of a crop yield even in a humid season as the harvest lacks time to ripen. Thus disadvantageous conditions for an ordinary plant development are established, and a crop yield of agricultural plants decreases or perishes.
Along with precipitation amounts, the number of days with precipitation a month or a year is also a significant climatic index. Plants are sensitive about a matter whether a given precipitation amount falls at once during only several days or it rains often and a precipitation amount is distributed comparatively evenly throughout a month. For instance, even one great downpour in a prairie area in summer has a little ability to improve an arid situation.
Employing a data set of a precipitation amount and a number of days one can calculate an accumulated precipitation amount for any region during a specific period of time.