It's simply surrealistic! The artist Salvador Dalí created a Taxi cab in which it rains inside. You can visit this hilarious cab in the courtyard of his house in Figueres, Northern Spain: https://en.wikipedia.org/wiki/Dal%C3%AD_Theatre_and_Museum
How hard is it to imagine a situation where this sentence might be used?
e.g. "Landlord: The roof is in good condition", "Tenant: It's raining in the kitchen!"
"I think a pipe has burst, it's raining in the kitchen"
"I like like camping and cooking outdoors, but sometimes it rains in the kitchen"
In the real world you will regularly encounter sentences which seem even stranger when they are heard out of context. That doesn't make them nonsense or mean they have no value in learning a language. Real conversations are full of analogies, similes, slang, poetic license - people infuse their conversation with these and more to make their accounts more interesting than a dry recital of facts. "There was a hole in the kitchen roof", becomes "We arrived home to find it was raining in the kitchen". The second is more amusing, more interesting and consequently less likely to bore the listener.
Also if you ask if the cat sat on the? I can guess the last word is mat. If you ask if the cat sat on moon it's more likely I'll have to genuinely have the word in my vocab. Logical sentences aren't necessarily the best way of learning words. People are so boringly linear.
I agree - the course writers must get a bit bored making up sentences for us basic students.