Hello and once again congrats for all your efforts.
Meteoblue provide the best forecasts, and your app is on its way to be way better than the meteoblue app. This is how I came across Sonuby.

One source of improvement is the representation of the daily forecast by one pictogram.
Well this is always a difficuly choice : we have 24 hourly pictograms each day. So how to summarize these 24 pictograms in one pictogram ?

Let me tell you that your current algorithm has lots of room for improvement.

In one example you will understand.
Wednesday 3 July, the picto for next Sunday in Toulouse , France, is "Showers"
The hourly forecast for the same day show : a shower between 0h00 and 1h00 during the night, and then a cloudy night, cloudy morning (but not overcast) , sunny afternoon, sunny evening.

So what should be chosen? Very difficlult isn't it? The only bad choice is to choose "showers" because it's less than hour (less than one hour) and besides, during the night. 
A good algorithm should determine the "average" weather during the day (probably a mix of clouds and sun pictogram). By the way : this is precisely what the Meteoblue does for the next Sunday.