This visualization displays temperature trends over time for multiple cities, with each city represented by a distinct colored line and labeled in a legend. The lines are smoothed using `curveBasis` and data is grouped by city via `d3.nest()`, while axes and scales are built with `d3.scaleTime`, `d3.scaleLinear`, and `d3.axisBottom`/`d3.axisLeft`. The color scale uses `d3.scaleOrdinal` with `schemeCategory10`, and the SVG rendering includes styled grid lines and a title. Data is loaded as CSV from an external URL.