MET Norway Weather API

What you can build

• Hold a Nordic shipment before the snow

  Locationforecast for the delivery address and Nowcast for the depot give an operator the next nine days and the next two hours. It proposes which orders to hold and for how long, and you approve the list.

  With Weather Hold

• Warn a shift before a red warning lands

  MetAlerts marks each warning yellow, orange, or red and says whether it is an Alert, Update, or Cancel. An operator drafts the notice for the sites inside the polygon and waits for your sign-off.

  With Severe Weather Notice

• Start the plant when the forecast says so

  Tomorrow's hourly temperature for the building's coordinate sets the pre-heat window. The operator proposes the start time; the change is sent once you approve it.

  With Optimal Start

• Protect coils on a freezing night

  A forecast minimum below zero at the site triggers a proposal to raise setpoints or run pumps overnight, with the forecast attached as the reason.

  With Freeze Protection

Requirements

• A User-Agent string with your application name and a contact address, sent on every request
• Coordinates truncated to four decimals; more precision returns 403 Forbidden
• A cache that keeps each response until its Expires time and re-requests with If-Modified-Since
• Clients that follow redirects, accept gzip, and use HTTPS
• Credit to MET Norway wherever the data is shown

Authentication

No key. Every request must carry a User-Agent header naming your application and a contact email or website; missing or generic agents get 403 Forbidden.

Limits

• Anything over 20 requests per second per application requires special agreement with MET Norway
• Nowcast covers only the Nordic area and depends on working radar coverage at the requested point
• MetAlerts filters by coordinate or Norwegian county number and covers MET Norway's own warning areas
• Mobile clients may poll at most once every 10 minutes for notifications and must not fetch while inactive

Questions and answers

Do I need an API key for api.met.no?

No. The API is open, but the Terms of Service require a User-Agent header that identifies your application and gives a contact email or website. Requests without one, or with a generic agent such as a library default, are answered 403 Forbidden. Fake identification strings lead to a permanent ban.

How far ahead does Locationforecast go, and where?

Nine days for any coordinate on earth. The compact endpoint returns the most used parameters; complete returns all values. Pass lat and lon with at most four decimals and, where you know it, altitude in whole metres.

How often may I poll?

Not before the time in the Expires header of the last response, and then with If-Modified-Since set to the Last-Modified value you stored. Nowcast updates every five minutes. Sustained traffic above 20 requests per second needs an agreement with MET Norway.