As you guessed, it surely is "It must be snowing in Germany", said in a very slangy way.
People usually don't use 雪る, but coining such verbs (even from traditional Japanese words) is not too uncommon among native speakers. You know, English speakers do it pretty often in casual settings, too. And in this case, there's a verb 曇【くも】る (雲 + る, "cloudy") which looks similar, so it should have been easy for them to come up with 雪る.
Of course, don't try to use it yourself until you reach the native speaker's level, or people would just think you made a grammatical mistake.