line chart with ChartJS

HTML

<script src="http://www.chartjs.org/assets/Chart.min.js"></script>
<canvas id="weeksChart" width="651" height="335"></canvas>

JavaScript

var dayTemperatureArray = [-5, 14, 15, 15, 17, 18, 19, 21, 22, 25, 24, 20, 19, 16];
var nightTemperatureArray = [-10, 4, 5, 6, 8, 11, 12, 15, 17, 15, 13, 12, 11, 9];

var dataWeeks = {
    labels: ["16.02", "17.02", "18.02", "19.02", "20.02", "21.02", "22.02", "23.02", "24.02", "25.02", "26.02", "27.02", "28.02", "01.03"],
    datasets: [{
        label: "Days temperature chart",
        fillColor: "transparent",
        strokeColor: "rgba(244, 6, 6, 1)",
        data: dayTemperatureArray
    }, {
        label: "Nights temperature chart",
        strokeColor: "#3f6bf5",
        data: nightTemperatureArray
    }]
};


var animationComplete = function () {
    var self = this;

    var tooltipColors = []
    Chart.helpers.each(self.datasets, function (dataset) {
        tooltipColors.push({
            fill: dataset.strokeColor,
            stroke: dataset.strokeColor
        })
    });

    Chart.helpers.each(self.datasets[0].points, function (point, index) {
        var labels = []
        var total = 0;
        Chart.helpers.each(self.datasets, function (dataset) {
            labels.push(dataset.points[index].value)
            total += Number(dataset.points[index].y);
        });

        new Chart.MultiTooltip({
            x: point.x,
            y: total / 2,
            xPadding: self.options.tooltipXPadding,
            yPadding: self.options.tooltipYPadding,
            xOffset: self.options.tooltipXOffset,
            fillColor: self.options.tooltipFillColor,
            textColor: self.options.tooltipFontColor,
            fontFamily: self.options.tooltipFontFamily,
            fontStyle: self.options.tooltipFontStyle,
            fontSize: self.options.tooltipFontSize,
            titleTextColor: self.options.tooltipTitleFontColor,
            titleFontFamily: self.options.tooltipTitleFontFamily,
            titleFontStyle: self.options.tooltipTitleFontStyle,
            titleFontSize: self.options.tooltipTitleFontSize,
            cornerRadius:...