This visualization plots monthly average temperatures recorded at San Francisco International Airport (SFO) from 1955 to 2020. Each semi-transparent circle represents a single month’s average temperature on a time-series axis, with a tooltip showing the exact value. The chart uses the Vega-Lite API and its `markCircle` encoding, with `vl.x().fieldT` for the date and `vl.y().fieldQ` for the temperature. Data is loaded via D3’s `csv` function from a NOAA-hosted GitHub gist, and the rendering is handled by Vega-Lite with custom axis styling from a config file.