National Weather Service (NWS) new API

NWS API has a bunch of changes coming 2017. The documentation is a little light right now, but it sounds like the old DWML/XML feeds are going away.  We will have to pull the data using the new API. Here is what I have learned about this new API so far while replacing the digitalDWML FcstType feed for my Illustrated Weather tool.

If you are using a Weather Service XML feed today and need someone to update it to, drop me an email.

National Weather Service API Streaming Setup

To stream anything from you must first set the stream header to include the Accept, Version and User-Agent. If you do not set the header the stream will return empty. NWS asks that you include your website and email address in the User-Agent so the they can contact you if need be.

$UserAgent = "YOURWEBSITE (";

// HTTP stream options:
$opts = array(
 'header'=>"Accept: application/geo+json;version=1\r\n" .
 "User-agent: $UserAgent\r\n"
$context = stream_context_create($opts);

After the header is set you can stream the /points/lat,lng URL into a json object and pull forecastGridData, which is the /gridpoints/office/x/y URL. If you do not need a detailed gridded forecast take a look at the /points/lat,lng/forecast/ or /points/lat,lng/forecast/hourly in the documentation.

$lat = 43.0204;
$lng = -71.6002;
$pointMetaUrl = "$lat,$lng";
$pointMetaFile = file_get_contents($pointMetaUrl, false, $context);
$pointMetaArray = json_decode($pointMetaFile, true);
$forecastGridData = $pointMetaArray["properties"]["forecastGridData"];

Now stream the detailed gridded forecast using the forecastGridData /gridpoints/office/x/y URL. Then start pulling the data you want.

$gridDataFile = file_get_contents($forecastGridData, false, $context);
$gridDataArray = json_decode($gridDataFile, true);
$temp = $gridDataArray["properties"]["temperature"]["values"];

Just about all weather elements returned, like temperature, are an array of arrays including a time and value (e.g. temperature). The time format is ISO 8601, plus a PHP  DateInterval. “PT2H”  is a 2 hour interval.  Temperatures are in Celsius.

"values": [
                    "validTime": "2017-02-17T08:00:00+00:00/PT2H",
                    "value": -6.1111111111111

Now all I have to do is retool my Illustrated Weather functions to deal with this new format. UGH!

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Kimball is a website designer and developer in Goffstown, NH.

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“National Weather Service (NWS) new API”

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