An area chart displays temperature in San Francisco over time, with a filled maroon region under a smooth curve. The visualization loads CSV data asynchronously via `d3.csv()`, parsing timestamps and numeric temperatures. It uses `d3.scaleTime()` and `d3.scaleLinear()` for axes, `d3.area()` with `curveBasis` for the smoothed shape, and `d3.axisBottom()` and `d3.axisLeft()` for labeled ticks.