The waterdrop made because vapor gets cold enters into cold air, and it generates by becoming a cryohydrate, growing up, and melting, when it falls. This is called "cold rain" with the rain which often falls to Japan. Unlike this, the rain which falls with waterdrop is called "warm rain."
In the Temperate Zone where most Japan belongs, the size of waterdrop is usually 0.1 mm to about 3 mm. However, in a weather report of Japan, a thing of 0.4 mm or less is classified not with rain but with "drizzle."
There is the word "rainfall eagerly longed for." Thus, rain is required for vegetable growth or people's life. If a plant does not have moisture, nutrition becomes less enough, and since crops (especially rice) do not grow if it does not rain, people will pose a problem in connection with death. Moreover, the water level of a river may be influenced by rain and coming-down change in which rain falls also influences the ecosystem of a river.
When rain is useful, it is required, but it may be made to be thought for a life of man that it is inconvenient. For example, in case of traffic, those who ride in a car from usually increase in number, and traffic congestion occurs easily.
Moreover, in the road, it becomes easy to slide under the influence of rain, and, thereby, fall accidents occur frequently.Moreover, the accidents which fall to a river or a waterway by rise of water of a river etc. may occur frequently.
Although there is no definition of rainfall etc., it expresses it as the case "heavy rain" in which the place leading to a disaster is restricted "where it begins to rain with a strong short time." This is the abnormal weather which rain progresses and happens.
It mainly happens from July to October in many cases, and suffers serious damage at various places.
For example, with the Tokai heavy rain which happened in September, 2000, Aichi, Mie, and Gifu made record heavy rain, and a rain quantity became twice the quantity which will come down in usual September in Nagoya on 1. Especially damage is serious in Gifu in which we live, and going home remembers that it was difficult from a kindergarten or a nursery school.
Change of the weather has had big influence on the function of the body. If especially a rainy day and cold day come, those who appeal against a pain with regards to the weather are in "an old wound aches" etc. If the pain is told that the fall of atmospheric pressure is related as the weather where it is affected and atmospheric pressure falls, a joint will expand and a pain will arise.