What’s Going On in This Graph? | New Normal U.S. Precipitation

How could the changes in “normal” precipitation affect you, your community, the United States and the world?

Here are some of the student headlines that capture the stories of these charts: “Where Time Is Ticking and Precipitation Is Hitting” by Tal of New York, “Without Hesitation, There Is Cause for Worry about Precipitation” by Kenyan of Mesa, Arizona, “Is America’s Rain Faucet Broken?” by Delali of Atlanta, “Precipitation Levels: Can You Predict the Future?” by Carlie of Chico, California, “Water Is Life, But Will the Excess of Precipitation Become a Threat to the US?” by Nat of CELA in Jalisco, Mexico and “Skies Above! Precipitation in America Over the Years” by Tessa of Andover, Massachusetts. It is surprising that no one used “normal” in their headline.

You may want to think about these additional questions:

  • See a world choropleth on the change in precipitation in the August 28, 2021 New York Times article “Tracking Two Americas: One Parched, One Soaked.” There is a comparison of annual average precipitation between 1984 – 2016 and the mid-20th century. What do you notice? What do you wonder? What surprises you? How will this affect us?

Next week’s graph about the relationship between vaccination rates and Covid hospitalization by state will be released by Friday, Sept. 24 with live-moderation on Wednesday, September 29. You can receive the 2021-2022 “What’s Going On In This Graph?” schedule by subscribing here to the Learning Network Friday newsletter. In the meantime, keep noticing and wondering. We welcome your online responses.


Below, we define mathematical and statistical terms and how they relate to this graph. To see the archives of all Stat Nuggets with links to their graphs, go to this index.


A choropleth map uses different shading, coloring or symbols within defined regions to indicate the values in these regions. The quantitative values are divided into intervals, which are shown on a key with their corresponding shading, coloring or symbols.

The U.S. Precipitation graphs are called choropleth maps. They display the percentage change in average precipitation between ten 30-year periods from 1901 to 2020 and the 20th century average. The differences are represented in colors with brown for percentage decreases and green for percentage increases. The darker the color, the greater the divergence from the 20th century average precipitation level. The percentage changes vary from less than -9.0% to more than +9.0%.


The average is a statistic that represents a central or typical value for a data set. There are different ways to measure the center, including the mean, which is the arithmetic average (the sum of all values divided by the number of values) and the median (the middle value when all values are ordered). Usually when “average” is used in the media, it is referring to the mean.

source: nytimes.com