flot threshold

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script src="https://rawgit.com/flot/flot/master/jquery.flot.js"></script>
<script src="https://rawgit.com/Codicode/flotanimator/master/jquery.flot.animator.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/flot/0.8.3/jquery.flot.time.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/flot/0.8.3/jquery.flot.threshold.js"></script>
<div id="chart1" style="width: 540px; height: 250px;">

JavaScript

var options = {
  "xaxis": {
    "mode": "time",
    "timeformat": "%d/%m"
  },
  "yaxes": [{
    "position": "left",
    "min": 98,
    "max": 100,
    "tickSize": 1
  }, {
    "position": "right",
    "min": 0,
    "max": 2
  }],
  "series": {
    "lines": {
      "show": true,
      "lineWidth": 3
    }
  },
  "colors": ["#008C00"],
  "legend": {
    "show": false
  },
  "grid": {
    "hoverable": true,
    "clickable": true
  }
};

  // data for dec 2015
  var data_ajax1 = {
    "lines": {
      "show": true,
      "lineWidth": 3
    },
    "points": {
      "show": false
    },
    "threshold": {
      "below": 99.50,
      "color": "#f25671"
    },
    "data": [{
      "0": 1451520000000,
      "1": 99.44
    }, {
      "0": 1451523600000,
      "1": 99.44
    }, {
      "0": 1451527200000,
      "1": 99.44
    }, {
      "0": 1451530800000,
      "1": 99.43
    }, {
      "0": 1451534400000,
      "1": 99.43
    }, {
      "0": 1451538000000,
      "1": 99.53
    }, {
      "0": 1451541600000,
      "1": 99.43
    }, {
      "0": 1451545200000,
      "1": 99.43
    }, {
      "0": 1451548800000,
      "1": 99.43
    }, {
      "0": 1451552400000,
      "1": 99.43
    }, {
      "0": 1451556000000,
      "1": 99.44
    }, {
      "0": 1451559600000,
      "1": 99.46
    }, {
      "0": 1451563200000,
      "1": 99.47
    }, {
      "0": 1451566800000,
      "1": 99.47
    }, {
      "0": 1451570400000,
      "1": 99.47
    }, {
      "0": 1451574000000,
      "1": 99.47
    }, {
      "0": 1451577600000,
      "1": 99.44
    }, {
      "0": 1451581200000,
      "1": 99.44
    }, {
      "0": 1451584800000,
      "1": 99.47
    }, {
      "0": 1451588400000,
      "1": 99.49
    }, {
      "0": 1451592000000,
      "1": 99.51
    }, {
      "0": 1451595600000,
      "1": 99.49
    }, {
      "0": 1451599200000,
      "1": 99.49
    }, {
      "0": 1451602800000,
      "1": 99.49
    }]
  };

  // data for jan 2016
  var data_ajax2 = {
    "lines": {
     ...