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What Is a Torrential Rain?

While there are only a few basic types of weather, including clear, cloudy, rain and snow, each of these types can be further broken down. When a meteorologist speaks of rain, for example, the rain may be classified as light, moderate or heavy. In some instances, the term "torrential rain" may be used to identify a particularly heavy downfall of rain.

Rain Amounts
- The amount of rain that qualifies as a torrential rain can vary depending on the source you use. According to Sky Rider for Kids, a heavy rainfall is anything more than 1/3-inch rainfall per hour. However, the National Weather Service categorizes a heavy rainfall as more than 1/2-inch rain per hour. Those who aren't meteorologists do not worry about the amount of rainfall, but rather what it looks like to the naked eye.
Visible Characteristics
- When a rainfall is considered torrential, it looks different than an average rainfall. If the rain is falling heavily enough, you may not be able to see more than a few feet in front of you. This can make for dangerous driving conditions, especially on open freeways. In torrential rains, the water also tends to pool in low-lying areas. The drops falling in torrential rains also tend to be larger and create a bigger splash in the puddles as it falls, which contributes to poor visibility.
Flooding
- Because the rain falls at larger quantities per hour in a torrential rainfall, flooding may become an issue, even in locations without a waterway. The sewer system often becomes overworked during a torrential downpour, which causes the water to run over the sewer grates rather than into them. Basements in homes may flood, especially in the absence of a working sump pump. Sewers may even back up into homes. Some of these floods are short-lived, while others last for days and even weeks.
Endurance
- The length of time in which a torrential downpour occurs can vary, but it is often short in endurance. Many storm systems remain in motion and the areas of heavier rainfall move on from one area to another at the same speed as the storm. However, in some cases, the storm may become stationary and dump large amounts of torrential rainfall in one location. In many storms, the amount of rain that falls per hour varies dramatically within the storm system. Areas of heavier downpours tend to be smaller and thus, their duration is shorter than that of the entire storm system.

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