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What’s Going On in This Graph? | Hotter Summers

Are summer nights getting hotter? How have minimum daily temperatures from June through August changed over the past 60 years in nine cities?

Notes:<br /> — Distributions show daily minimum temperatures for the summer months (June – August) in each decade at airport weather stations. <br /> — Nights are considered abnormally cold or hot based on the 5th and 95th percentile of the 1960s temperatures. <br /> — Temperature ranges for each chart are scaled to the summer nighttime temperature ranges for each city.

These graphs of summer daily minimum temperatures were published in The New York Times. Examine the notes below the graph and the explanations on the Phoenix graph that apply to all of the graphs to best understand what the graph shows.

On Wednesday, May 4, we will moderate your responses live online. By Friday morning, May 6, we will provide the “Reveal” — the graphs’ free online link, additional questions, shout outs for student headlines and Stat Nuggets.

1. After looking closely at the graph above (or at this full-size image), answer these four questions:

  • What do you notice?

  • What do you wonder?

  • How does this relate to you and your community?

  • What’s going on in this graph? Create a catchy headline that captures the graph’s main idea.

The questions are intended to build on one another, so try to answer them in order.

2. Next, join the conversation online by clicking on the comment button and posting in the box. (Teachers of students younger than 13 are welcome to post their students’ responses.)

3. Below the response box, there is an option to click on “Email me when my comment is published.” This sends the link to your response which you can share with your teacher.

4. After you have posted, read what others have said, then respond to someone else by posting a comment. Use the “Reply” button to address that student directly.

On Wednesday, May 4, teachers from our collaborator, the American Statistical Association, will facilitate this discussion from 9 a.m. to 2 p.m. Eastern time.

5. By Friday morning, May 6, we will reveal more information about the graph, including a free link to the article that includes this graph, at the bottom of this post. We encourage you to post additional comments based on the article, possibly using statistical terms defined in the Stat Nuggets.

Updated: MAY 5, 2022

The Reveal

These graphs appeared in the Sept. 13, 2021 print version of The New York Times article “Why We’re Experiencing So Many Unusually Hot Summer Nights.” The graphs are “smoothed” histograms (see Stat Nugget below) of the summer minimum daily temperatures. The interactive online version allows you to input U.S. cities which are nearby airports (where the data is collected) to view the animation of the 1960 – 2020 histograms of the airport’s temperatures.

There has been much written about how average temperatures worldwide are at all time highs. Another way to examine temperatures is to look at the minimum night temperatures. In the 1960s, the distribution of these temperatures was approximately normal. Across the country, nights are warming faster than days because of global warming and increased urbanization. This is physically taxing on people who might not get the opportunity to cool down in the evening. With the number of extremely hot nights increasing the fastest, the distribution of temperatures are shifting to the right and becoming more skewed. (See Stat Nuggets below for normal and skewed distributions.) Experiencing extremely hot temperatures is more frequent and more damaging, especially in cities where some cannot afford air-conditioning. Heat waves cause deaths disproportionate for residents of lower-income communities.

Here are some of the student headlines that capture the stories of this graph: “Is Global Warming that Big of a Deal? This Graph May Tell You!” by Samuel of Derby, Kansas; “Climate Change, Nightly Warming” by Ronny of Perth Amboy High School in N. J.; “The Quick and Steep Incline for Summer Temps” by Evan of N.H.; “Summer Sizzles” by Ashley of N.Y., “The Crazy Thing Climate Change Has Done To Our Summers” by Irina of Mass.; “It’s Getting Hot and It Won’t Stop” by Serena and “Hot Summer Nights” by Cierra.

You may want to think about these additional questions:

  • Based on the graphs, which cities have gotten the most abnormally hot since 1960? Which cities have gotten the most abnormally cold since 1960?

  • Except for Houston, the peaks for the 2020s of all cities are all greater than for the peaks of the 1960s. What does this signify?

  • If the article is about how much hotter summer temperatures are, why do you think the journalist shows the summer minimum daily temperatures rather than the summer maximum daily temperatures? (The answer relates to the note below the graph: “Nights are considered abnormally cold or hot based on the 5th and 95th percentile of the 1960s temperatures.” See Stat Nugget below for percentile.)

  • The graphs below appeared in the July 20, 2021 New York Times article “Extreme Summer.” The graph’s arrows compare the July 1970 and July 2020 average high temperatures. What do you notice from these graphs? How do they relate to the findings from the distributions above?

  • How are the night temperatures in your area trending? Go to the article to see the histograms for seven decades for the city with an airport that is nearest to you. Input the city and click to see an animation of the histograms from the 1960s to 2020s. What do you notice about the changes in average summer night temperatures, range of summer night temperatures and the proportion of unusually cold and unusually hot summer night temperatures? You can compare your findings to other U.S. cities.

Keep noticing and wondering. We continue to welcome your online responses.

The next graph on change in teen behaviors between 1989 and 2019 will be released by Friday, May 6 with live-moderation on Wednesday, May 11. You will be able to receive the 2022-2023 “What’s Going On In This Graph?” schedule by subscribing here to the Learning Network Friday newsletter.


Stat Nuggets for “Why We’re Experiencing So Many Unusually Hot Summer Nights”

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.


The distribution of a quantitative variable describes how the values of the variable are distributed along the number line.

In the Hot Summers graphs, the quantitative variable is the summer night daily minimum temperatures for the decades 1960 – 2020. The x-axis displays temperatures in degrees Fahrenheit. The y-axis displays the percentage of the total number of summer nights minimum temperatures for each degree Fahrenheit. For all nine cities from 1960 to 2020, the average temperature for summer nights increases, as seen from the shifting of the histogram to the right.


A histogram displays the distribution of a quantitative variable by showing the frequency (count) or relative frequency (percentage) of the values that fall in specific intervals. The intervals are along the x-axis. Bars drawn above the corresponding intervals represent the frequency or relative frequency of values falling in each of the intervals. These numbers or percentages are shown on the y-axis.

A smoothed histogram is a curve that is drawn over a histogram to show the general shape, center and spread of the distribution.

The Hot Summer graphs are smoothed histograms, showing distributions of the relative frequencies of summer minimum daily temperatures for the 1960s and 2020s. The distribution is shown as a continuous curve, rather than a histogram with bars, to show a general shape rather than specific percentages.


A normal distribution is a bell-shaped symmetric distribution (as if reflected in a mirror) with one peak (or unimodal). A skewed distribution is also unimodal but is asymmetric (not symmetric) with a longer “tail” in the direction of its skew.

The Hot Summer histograms are unimodal. Though somewhat symmetric and approximately normal in the 1960s, the graphs tend to be skewed left signifying more extreme hot summer night temperatures.


Percentiles are numbers that divide ordered, quantitative datasets or distributions into one-hundredths. After putting data in order from smallest to largest, you can find the percentiles. For example, for the 90th percentile, 10% of the data are greater than this value and 90% of the data is less than this value.

The Hot Summer graphs, temperatures are considered abnormally cold or hot if they are less than the 5th percentile or greater than the 95th percentile. Temperatures that are abnormally cold are those that are less than 95% of the summer minimum daily temperatures in the 1960s. Temperatures that are abnormally hot are those that are greater than 95% of the summer minimum daily temperatures in the 1960s. The values of the percentiles vary among cities since the summer minimum daily temperatures are different among cities.


The graph for “What’s Going On in This Graph?” is selected in partnership with Sharon Hessney. Ms. Hessney wrote the “reveal” and Stat Nuggets with Roxy Peck, professor emerita, California Polytechnic State University San Luis Obispo, and moderates online with Annie Fetter, a creator and promoter of “What do I notice? What do I wonder?”


• See all graphs in this series or collections of 60 of our favorite graphs, 28 graphs that teach about inequality and 24 graphs about climate change.

• View our archives that link to all past releases, organized by topic, graph type and Stat Nugget.

• Learn more about the notice and wonder teaching strategy from this 5-minute video and how and why other teachers are using this strategy from our on-demand webinar.

• Sign up for our free weekly Learning Network newsletter so you never miss a graph. Graphs are always released by the Friday before the Wednesday live-moderation to give teachers time to plan ahead.

• Go to the American Statistical Association K-12 website, which includes teacher statistics resources, Census in the Schools student-generated data, professional development opportunities, and more.

Students 13 and older in the United States and the Britain, and 16 and older elsewhere, are invited to comment. All comments are moderated by the Learning Network staff, but please keep in mind that once your comment is accepted, it will be made public.

You are watching: Hotter Summers – The New York Times. Info created by GBee English Center selection and synthesis along with other related topics.