I think you will find this very frustrating. I have examined multiple weather providers, and found that none of them agree with each other. And none of them actually match the real conditions at my home. I live near the coast, and even a mile further from the ocean can vary the temperature by many degrees.
The (US) National Weather Service is the only provider I know of that is free. Private weather providers always require an individual "API key", and they charge for useage. Some of the providers will have a free tier for private individuals (some more generous than others). But a Allonis API key would be considered commercial, and cost money. And Allonis would have a lot of development costs, as each provider gives the weather information differently, and Allonis would have to code for each one.
None of the providers I have found give accurate results for where I live. So I have resorted to using three different providers to get the best information from each. The NWS provides the best forecast information for my lcoality, and my source for weather alerts. I use Open Weather Map to get the current conditions. But since their source is at a nerby airport where conditions are different, I have an Ambient Home weather station for my local temperature, wind and rain. I have an Android tablet for use with my Home Automation (Homeseer) that also polls the three sources (using Tasker), and then forwards the information to Homeseer. The technique I use to forward the information would be very easy to do for Allonis as well, but I never saw the need.
A couple of weeks ago I started looking at Google Weather as a provider. I have been running both Open Weather Map and Google weather side by side, to compare between the two. I would say that they are in agreement with the temperature and wind about 80% of the time (this is summer, we don't have rain at this time of the year). As far as conditions (clear/sunny or percent cloudy), they only exactly agree about 20% of the time.
I think if you are looking for accurate weather, then you might investigate getting a home weather station such as Ambient, which will be condiderably more accurate for your home than any weather provider. There are seveal ways then to get the information transfered into Allonis.