To answer your question, if you want to obtain raw sensor data our government (and some volunteers) maintains a network of thousands of weather stations. Many are automated, many are people doing manual obs. If you know how to write code you can programmatically obtain these data.

However you might be confused... climacell does forecasts and you asked about finding station data? They are completely different things. I have no insight into what climacell does but i am a knowledge person in industry. I can tell you that nobody has some groudnbreaking 'AI' machine learning algorithm that is amazingly great at forecasting weather. If such a thing did exist, that person would have zillions of dollars because they can accurately predict weather better then anyone else.