So, this checks off a couple of my favorite requisites for a good teaching example: You can personalize it, it is contemporary and applicable, it illustrates a few different sorts of statistics.
Climate Central wrote this article about first frost dates, and how those dates, and an increasing number of frost free days, create longer growing seasons.
The overall article is about how frosty the US is becoming as the Earth warms. They provide data about the first frost is a number of US cities. It even lists my childhood hometown of Altoona, PA, so I think there is a pretty large selection of cities to choose from. Below, I've included the screen grab for my current home, and the home of Gannon University, Erie, PA.
First frost date illustrated with a line chart, but the chart also includes the regression line.
|Data for frosty, chilly Erie, PA|
The article also presents a chart that shows how frost is related to the length of growing season in the US. This graph is a good example as the y-axis shows the number of days above or below average growing season over time, starting with 1895 and going through 2015.
Both graphs also illustrate long term data collection, and illustrate archival data.