折线图显示不正确echarts 配置项内容和展示

折线图Y轴值更少的显示在大的上边，比如这里平均温度比最低温度大但是却显示在最低温度下边

      option = option = {
    "title": {
        "text": "温度"
    },
    "tooltip": {
        "trigger": "axis"
    },
    "legend": {
        "data": ["最高温度", "最低温度", "平均气温"]
    },
    "grid": {
        "left": "3%",
        "right": "4%",
        "bottom": "3%",
        "containLabel": true
    },
    "toolbox": {
        "feature": {
            "saveAsImage": {}
        }
    },
    "xAxis": {
        "type": "category",
        "boundaryGap": false,
        "data": ["2019-1-1", "2019-1-2", "2019-1-3", "2019-1-4", "2019-1-5", "2019-1-6", "2019-1-7", "2019-1-8", "2019-1-9", "2019-1-10", "2019-1-11", "2019-1-12", "2019-1-13", "2019-1-14", "2019-1-15", "2019-1-16", "2019-1-17"]
    },
    "yAxis": {
        "type": "value"
    },
    "series": [{
        "name": "最高温度",
        "type": "line", 
        "data": [5.7, 8.6, 4, 3.8, 8.7, 8.3, 8.9, 3.7, 4.6, 3, 6.9, 7.7, 8.8, 8.7, 5.1, 7.1, 9.3]
    }, {
        "name": "最低温度",
        "type": "line", 
        "data": [-12.4, -13.3, -7.6, -8.4, -13.4, -11.3, -10.8, -6.7, -5.2, -7.8, -11.2, -11.2, -10.8, -9.4, -13.5, -13.3, -14.2]
    }, {
        "name": "平均气温",
        "type": "line", 
        "data": [-3.7, -4.1, -2.3, -2.2, -4.3, -2.3, -1.7, -2.1, -1.8, -3, -3.1, -2.3, -1.2, -0.8, -4.6, -4.3, -3.3]
    }]
}