The Data Asset eXchange (DAX) is a curated open data repository for free data sets from IBM Research and third parties. To learn more about DAX take a look at the official Get started with the Data Asset eXchange tutorial.
The JupyterLab and Elyra tutorial utilizes the NOAA Weather Data - JFK Airport dataset, which is complemented by a set of notebooks that you can download and run here.
If you'd like to explore other interesting datasets, take a look at: