[Solved]-HighChart Heatmap with JSON data-Highcharts

You need to convert that to the col/row point instead of date string. You are going to have 2 category axis: x and y. Then the index of x/y axis becomes the [x, y, value]. So, if your data starts on "2013-04-01" then it is your first index such that [ ["2013-04-01",0,-0.7], ["2013-04-02",0,-3.4], ["2013-04-03",0,-1.1] ] becomes:

[ [0,0,-0.7], [1,0,-3.4], [2,0,-1.1] ]

Note that this is just one row's worth of data. What is your y component?

EDIT: If your yAxis component will be the hour of the day then you would set up your axii like so:

xAxis: {
    categories: ['2013-04-01', '2013-04-02', '2013-04-03'],
    labels: {
        rotation: 90
    }
},
yAxis: {
    title: {
        text: null
    },
    labels: {
        enabled: false
    },
    categories: ['Midnight', '1 am', '2 am', '3 am', '4 am', '5 am', '6 am', '7 am', '8 am', '9 am', '10 am', '11 am', 'Noon', '1 pm', '2 pm', '3 pm', '4 pm', '5 pm', '6 pm', '7 pm', '8 pm', '9 pm', '10 pm', '11 pm'],
    min: 0,
    max: 23,
    reversed: true
},

Then you series would look something like:

series: [{
    borderWidth: 0,
    nullColor: '#EFEFEF',
    data: [ [0,0,-0.7], [1,0,-3.4], [2,0,-1.1] ]
}]

Live demo.

There are other items I added there that I will let you figure out (why do I set reversed: true, what is the colorAxis, etc). The important thing to note is that the series.data format is different from any other highchart setup.