Edit in JSFiddle

$(function () {
    var tempDb = {
        'tokyo': [
            {'feellike': -1, 'detail': 'Cloudy'},
            {'feellike': -2, 'detail': 'Sunny'},
            {'feellike': -6, 'detail': 'Cloudy'},
            {'feellike': -7, 'detail': 'Sunny'},
            {'feellike': -8, 'detail': 'Foggy'},
        ],
        'newyork': [
            {'feellike': -2, 'detail': 'Sunny'},
            {'feellike': -3, 'detail': 'Foggy'},
            {'feellike': -6, 'detail': 'Cloudy'},
            {'feellike': -7, 'detail': 'Sunny'},
            {'feellike': -8, 'detail': 'Foggy'},
        ],
        'berlin': [
            {'feellike': -2, 'detail': 'Sunny'},
            {'feellike': -3, 'detail': 'Foggy'},
            {'feellike': -4, 'detail': 'Funny'},
            {'feellike': -5, 'detail': 'Rainy'},
            {'feellike': -6, 'detail': 'Cloudy'},
        ],
        'london': [
            {'feellike': -4, 'detail': 'Funny'},
            {'feellike': -5, 'detail': 'Rainy'},
            {'feellike': -6, 'detail': 'Cloudy'},
            {'feellike': -7, 'detail': 'Sunny'},
            {'feellike': -8, 'detail': 'Foggy'},
        ]
    };
    $('#container').highcharts({
        title: {
            text: 'Monthly Average Temperature',
            x: -20 //center
        },
        subtitle: {
            text: 'Source: WorldClimate.com',
            x: -20
        },
        xAxis: {
            categories: ['Apr', 'May', 'Jun',
                'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
        },
        yAxis: {
            title: {
                text: 'Temperature (°C)'
            },
            plotLines: [{
                value: 0,
                width: 1,
                color: '#808080'
            }]
        },
        tooltip: {
         formatter: function() {
             var i = this.series.data.indexOf( this.point ),
                 data = tempDb[this.series.options._id][i];
        
             /* 
              * You definitly will want to check for 
              * null / undefine here before output
              */ 
             
             return '<b>' + this.series.name + '</b>' +
                 '<br />Country: ' + this.series.options.country + 
                 '<br />Month: ' + this.x + 
                 '<br />Temperature: ' + this.y +'°C' + 
                 '<br />Feel like: ' + data.feellike +'°C' + 
                 '<br />Detail: ' + data.detail;
         }
        },
        legend: {
            layout: 'vertical',
            align: 'right',
            verticalAlign: 'middle',
            borderWidth: 0
        },
        series: [{
            name: 'Tokyo',
            data: [14.5, 18.2, 21.5, 25.2, 26.5],
            country: 'Japan',
            _id: 'tokyo'
        }, {
            name: 'New York',
            data: [11.3, 17.0, 22.0, 24.8, 24.1],
            country: 'USA',
            _id: 'newyork'
        }, {
            name: 'Berlin',
            data: [8.4, 13.5, 17.0, 18.6, 17.9],
            country: 'German',
            _id: 'berlin'
        }, {
            name: 'London',
            data: [8.5, 11.9, 15.2, 17.0, 16.6],
            country: 'UK',
            _id: 'london'
        }]
    });
});

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