repeat1.vl

{
    "data": {
        "url": "https://vega.github.io/vega-lite/data/weather.csv"
    },
    "repeat": {
        "column": [
            "temp_max",
            "precipitation",
            "wind"
        ]
    },
    "spec": {
        "layer": [
            {
                "mark": "line",
                "encoding": {
                    "color": {
                        "field": "location",
                        "type": "nominal"
                    },
                    "opacity": {
                        "value": 0.2
                    },
                    "x": {
                        "field": "date",
                        "timeUnit": "month",
                        "type": "ordinal"
                    },
                    "detail": {
                        "field": "date",
                        "timeUnit": "year",
                        "type": "temporal"
                    },
                    "y": {
                        "field": {
                            "repeat": "column"
                        },
                        "aggregate": "mean",
                        "type": "quantitative"
                    }
                }
            },
            {
                "mark": "line",
                "encoding": {
                    "color": {
                        "field": "location",
                        "type": "nominal"
                    },
                    "x": {
                        "field": "date",
                        "timeUnit": "month",
                        "type": "ordinal"
                    },
                    "y": {
                        "field": {
                            "repeat": "column"
                        },
                        "aggregate": "mean",
                        "type": "quantitative"
                    }
                }
            }
        ]
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "description": "Monthly weather information for individual years and overall average for Seatle and New York"
}