Special character error despite UTF-8 get °C instead of °C

Question

In my fiddle https://jsfiddle.net/quito96/jaeL8wf0, the label for temperature, °C, looks good. Implemented on my website: https://steinhagen-wetter.de/vorhersage. I have an encoding failure and get sign  before °C. HTML code looks like: <script src="meteogram.js" type="text/javascript " content="application/json;charset=UTF-8"></script>.

I have also tried with content="text/html; charset=UTF-8. The results are the same. The file meteogram.js is also formatted as UTF-8.

Any suggestions?

Full HTML:

<script src="https://code.highcharts.com/highcharts.js"></script>
<script src="https://code.highcharts.com/modules/data.js"></script>
<script src="https://code.highcharts.com/modules/pattern-fill.js"></script>
<script src="https://code.highcharts.com/modules/exporting.js"></script>
<script src="https://code.highcharts.com/modules/windbarb.js"></script>
<script src="https://code.highcharts.com/modules/accessibility.js"></script>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript"></script>
<link href="https://netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css" rel="stylesheet">

<figure class="highcharts-figure">
    <div id="container">
        <div id="loading">
            <i class="fa fa-spinner fa-spin"></i> Loading data from external source
        </div>
    </div>


<script src="meteogram.js" type="text/javascript " content="application/json;charset=UTF-8"></script>

<button type="button" id="myBtn" onclick="location.href='https://steinhagen-wetter.de'" class="button" text="Home"><i class="fa fa-home " ></i></button>

</figure>