"It is raining around the boy."
Translation:Det regner omkring drengen.
I don't like comparing Danish to English usually, but here it works. If you were to use "er" like that in this sentence it would be like saying "It is rains around the boy". Danish doesn't distinguish between when someone "does" something and someone "is doing" something in the same way as English does. It is common in Danish to use the simple present tense for both of these situations like it does here.