Jáchym, you say you dont have a station that records solar, what about a station that can have extra temp sensors? If so and if you use a program like weather display, you could make your own solar sensor with the Solar in a Jar method, it works very well and i used it for a good few years and even experimented with the idea, such as a drilled out lightbulb, whilst very sensitive to sunlight, ie recorded every single subtle change, i changed to a laboratory flask shaped like a bulb and a temp probe and placed it upside down on my mast, i cant remember why i ditched the lightbulb idea now. Good thing is, it can also be doubled as a night cloud too.Ok, I'm rambling on and you may not even be able to use extra temp sensors...