A multi-line time-series chart displays temperature readings across several cities, with each city’s data drawn as a colored, semi-transparent smooth curve. The visualization uses d3.scaleTime, d3.scaleLinear, d3.nest, and d3.line with curveBasis to generate the paths in an SVG. Data comes from a CSV file loaded via d3.csv, and axes are rendered using d3.axisBottom and d3.axisLeft with gridlines.