Well from what i can tell after playing the game for (64 days ingame) ,it started to rain
and its raining...still -_- , even still the weather forecast ingame from what i can understand its taken from 4 weather stations in the area and the forecast is bleak more RAIN
...anyway im in mid spring ( ingame and to be honest the weather isnt as nice and sunny as when the game started. )
So from what i can tell , form my experience in story mode the weather is somewhat dynamic its been raining for 3 days now non stop although not at the same intensity i noticed im using max settings ingame, the snow in rnr is like rain if you pause the game you can see the tiny snow flakes , other than that you dont actually see snow on the road surface only some textures on hills/mountains.