AccuWeather

Register on the AccuWeather site.
Next, register a new application. I just named it Personal, marked it as Limited Trial, Internal App, Business to Consumer. Once you do this you'll get an API Key, save it.

You'll also need an AccuWeather Location Key.
Do a normal AccuWeather search for your location. The last number in the URL is the Location Key. In the example of London, it's 328328.

In config.toml, choose to use the AccuWeather provider by adding it under the [weather] section:

[weather]
... your location details from the location step ...
provider = "accuweather"

Then add a section for the AccuWeather provider with your API key and location key.

[weather.providers.accuweather]
api_key = "xxxxxx"
location_key = "328328"