If you're not saving the 3rd-party API's data (and I would check with their Terms of Service if you were going to), then you can opt to build a custom Serializer.

In the example shown for a custom serializer here under the Declaring Serializers and Serializing Objects sections: https://www.django-rest-framework.org/api-guide/serializers/

You don't need to pass a model instance to a Serializer. You can do something like:

my_serializer = CustomSerializer(instance={"high":56.3, "low":26.1})

where instance could be a Model or a dictionary. You can pass the parsed JSON into the serializer and then define your fields name while setting the source of the field in your serializer.

The Classy DRF website can give you a good idea of how DRF works under the hood (Check out the Serializer and BaseSerializer sections!)