A line chart displays temperature readings over time, with a tooltip that reveals the exact temperature on hover. The visualization is built using the Vega-Lite API, which translates a concise specification into a rendered Vega graphic. Data is loaded from a CSV file of San Francisco weekly temperatures via the `d3.csv` method. The chart's appearance, including axis styling and label fonts, is customized through a configuration object, and the visualization resizes to fit the browser window.