This heatmap displays average monthly temperatures for ten cities across 2016, using a vertical color gradient from the Inferno interpolator to encode temperature values. The visualization employs D3.js v6 with SVG rendering, scaling months along the x-axis and cities along the y-axis. Interactive tooltips reveal exact temperature values on hover, while a d3-legend color scale provides a visual reference for the temperature range. The data comes from a CSV file loaded via d3.csv, with rounded cell corners and opacity styling for clarity.