Translation:There is risk of thunderstorm on Tuesday.
This is not natural English. I answered 'There is thunderstorm risk on Tuesday' which whilst not ideal, is better than the only accepted answer. Better would have been 'There is a thunderstorm risk on Tuesday' but there was no 'a' tile available. More natural would have been 'There is a risk of a thunderstorm on Tuesday', as others have mentioned. Alternatively, it should have been 'There is (a) risk of thunderstorms on Tuesday'.
Another example of a poorly constructed course question losing me another Health point/life. Very irritating!
In addition to the other problems in this sentence that users have pointed out, English speakers would also never say "risk" in this sentence. We'd say "There is a chance of thunderstorms on Tuesday."
The word "risk" doesn't just mean "chance of a bad thing happening." It means "chance of a bad thing happening based on a choice." The likelihood of a thunderstorm is not based on anyone's decision; it's just something that either will or won't happen. But if someone decides to drive through the storm, that person is taking a risk.