As seen on the screenshots below, the sun will shine through the clouds and cast shadows no matter what weather settings you have. It's always sunny in the rain or fog, which is very annoying and immersion breaking. As a result, I can't drive on Tharandter Rampe with any other weather but clear. The same problem can be observed on Nahverkehr Dresden. I'm reporting this in the hopes that it won't appear on future routes. All the screenshots are taken at "full clouds"
Well, I'm not surprised. There are several other unresolved light and shadow issues, two of which are particularly prevalent at night: multiple vertical beams of light at several stations on HRR and other routes, and the overhead lights at Elkhorn on CRR that allow light to shine through the cab ceiling. And of course lighting in tunnels is not fixed yet and probably never will be. Obviously there are too many different problems here, I'll just mention two: the LOD range leading to sunlit rails in the tunnel, and certain indeterminable light sources that mysteriously cast light into the cab in an unlit tunnel.
There are many things wrong with the lighting. I wonder if this will ever get fixed. Now should be the time since it was said that the time after SOS would be a time to fix long standing issues and bugs.