layer4.vl

{
    "data": {
        "url": "https://vega.github.io/vega-lite/data/seattle-weather.csv"
    },
    "resolve": {
        "scale": {
            "y": "independent"
        }
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "layer": [
        {
            "mark": "bar",
            "encoding": {
                "y": {
                    "field": "precipitation",
                    "aggregate": "mean",
                    "type": "quantitative",
                    "axis": {
                        "grid": false
                    }
                }
            }
        },
        {
            "mark": "line",
            "encoding": {
                "color": {
                    "value": "firebrick"
                },
                "y": {
                    "field": "temp_max",
                    "scale": {
                        "zero": false
                    },
                    "aggregate": "mean",
                    "type": "quantitative",
                    "axis": {
                        "grid": false
                    }
                }
            }
        }
    ],
    "encoding": {
        "x": {
            "field": "date",
            "timeUnit": "month",
            "type": "ordinal"
        }
    },
    "description": "Layered bar/line chart with dual axes"
}