The plane has condensation marks (white smoke-). Is it going to rain soon? Or will it get cold?

Not necessarily. The cruising altitude of the plane is about 10000 meters, and the temperature can be as low as MINUS 60 degrees. The hot air ejected by turbofan engine changes physically with the water vapor ice crystals in the air, and then it is cooled by the evaporated low-temperature air, resulting in the wake. It is a normal phenomenon, which does not necessarily mean that it will rain. Of course, when the air humidity is high or the temperature is low, the wake will be more obvious.