FAQ #4678

Have a question? Try asking one of our Experts

Large rains―such as those accompanying a hurricane or nor'easter―often are called a two-year, five-year, or even 100-year storm. What does that mean?

Related resource areas: Agrosecurity and Floods

A two-year storm is one that has the statistical likelihood of occurring every two years on average. In other words, it has a 50% chance of occurring in any given year. It is based on statistical analysis of long-term precipitation data.

Similarly, a 10-year storm has a 10% chance of occurring in any given year, and a 100-year storm has a 1% chance of occurring in any given year.

It does not mean that if a 10-year rainfall comes in 2006 we won't see one again until 2016. There could be three 10-year storms in three years, however unlikely. Similarly, there could be a 30-year period without a 10-year storm, which is also unlikely.

Have a specific question? Try asking one of our Experts

Unlike most other resources on the web, we have experts from Universities around the country ready to answer your questions.

Comments

Post a comment about this topic

Please keep comments on topic. To ask a question, please use Ask an Expert. All comments are held for moderation. Comments that include profanity, personal attacks or other inappropriate material will not be posted to the site.

Did you find this page useful?

No one has rated this article yet. Why not be the first? what is this?
not useful
very useful
 1  2  3  4  5