This example displays monthly temperature variations for four U.S. cities—NYC, LA, Chicago, and Houston—as small multiples of line charts, with dots marking each data point and a color-coded legend. Hovering over a dot enlarges it and shows the exact temperature value as a tooltip. The code uses D3 v7’s `d3.csv`, `d3.scaleBand`, `d3.scaleLinear`, `d3.line`, and `d3.axisBottom`/`d3.axisLeft` to render SVG charts, with data pulled from a GitHub-hosted CSV file. A `d3.legendColor` scale generates the legend, and the visualization is built with React in a single HTML file.